I am creating a linked list but after printing it I am only getting the last element in an unending loop here is the code Link to my code my linked List
#include<iostream>
using namespace std;
struct node{
int data; // for data component
node* next; // to hold addr of next
}*head_first=NULL;
void create(int* a, int n) // a is array and n is sizeof
{
node *newnode,*temp;
newnode=new node();
for(int i=0;i<n;i ){
newnode->data=a[i];
newnode->next=NULL;
if(head_first==NULL){
temp=head_first=newnode;
cout<<"head assigned"<<endl;
}
else{
temp->next=newnode;
temp=newnode;
cout<<i<<" node created"<<endl;
}
}
}
void dis(node *p){
while(p!=NULL){
cout<< p->data <<endl;
p=p->next;
}
}
int main(){
int a[]={10,20,30,40,50,60};
int size=sizeof(a)/sizeof(int);
create(a,size);
dis(head_first);
return 0;
}
CodePudding user response：
Aside of the raw pointer and nullptr issue, I noticed that your node points itself. I think the code have to be modified like this:
void create(int* a, int n) // a is array and n is sizeof
{
node *newnode,*temp;
for(int i=0;i<n;i ){
newnode=new node();
newnode->data=a[i];
newnode->next=NULL;
if(head_first==NULL){
temp=head_first=newnode;
cout<<"head assigned"<<endl;
}
else{
temp->next=newnode;
temp=newnode;
cout<<i<<" node created"<<endl;
}
}
}
CodePudding user response：
#include<iostream>
using namespace std;
struct node{
int data; // for data component
node* next; // to hold addr of next
}*head_first=NULL;
void create(int* a, int n) // a is array and n is sizeof
{
node *newnode,*temp;
newnode=new node();
for(int i=0;i<n;i ){
newnode=new node();
newnode->data=a[i];
newnode->next=NULL;
if(head_first==NULL){
temp=head_first=newnode;
cout<<"head assigned"<<endl;
}
else{
temp->next=newnode;
temp=newnode;
cout<<i<<" node created"<<endl;
}
}
}
void dis(node *p){
while(p!=NULL){
cout<< p->data <<endl;
p=p->next;
}
}
int main(){
int a[]={10,20,30,40,50,60};
int size=sizeof(a)/sizeof(int);
create(a,size);
dis(head_first);
return 0;
}
You have used same reference that's reason code always update same memory location value and finally give last value
CodePudding user response：
I think the errors that you get, are of course resulting from some wrong coding implementation. And those have been corrected already in other answers.
But for me the biggest problem is the wrong design.
Obviously you are mixing up "Node" with the "linked list". In real world applications the "Node" is a part of a linked list. In object oriented language we have a "has a" relation. So, a linked list has a Node.
Additionally, the whole "Node" functionality would be encapsulated in the linked list. So, the "Node" would NOT be visible to the outside world.
If we interact with a linked list to store or retrive values and such, we would never know about (and even not be interested in) the internas like a "Node".
And, maybe because of that suboptimal design approach, you will create errors.
So, maybe it would be a good idea to refactor your design, and after that, implement it in some better way. For example, use classes, no global avariables and no free functions to operate on list data.
To give you an idea on what could be done, I will show you some implementation of a singly linked list and a double linked list.
Singly Linked List:
#include <iostream>
#include <iterator>
#include <initializer_list>
#include <algorithm>
// Very simple implementation of a forward list
template <class T>
class SinglyLinkedList {
// The node
struct Node {
T data{}; // Data. Would normally be a templated argument
Node* next{}; // And the pointer to the next node
Node(const T& i, Node* n = nullptr) : data(i), next(n) {}; // Simple constructor to set a value and next pointer
};
Node* head{}; // This is the start of the list
// It would be advisable to have a tail pointer. We use the more inefficient approach here
Node* getLast() const { Node* n{ head }; while (n and n->next) n = n->next; return n; }
public:
// Constructor / Destructor --------------------------------------------------------------------------------------------------------
~SinglyLinkedList() { clear(); }
// Default constuctor
SinglyLinkedList() {} // Default
// From an initialization list
SinglyLinkedList(const std::initializer_list<T>& il) { clear(); for (const T& i : il) push_back(i); } // From initializer list
// Copy constructor
SinglyLinkedList(const SinglyLinkedList& other) { clear(); for (const T& i : other) push_back(i); }
// Move constructor. Will steal the elements from the other
SinglyLinkedList(SinglyLinkedList&& other) noexcept { head = other.head; other.head = nullptr; }
// Assignment operator
SinglyLinkedList& operator = (const SinglyLinkedList& other) { clear(); for (const T& i : other) push_back(i); }
// Move assignment operator
SinglyLinkedList& operator = (SinglyLinkedList&& other) { head = other.head; other.head = nullptr; }
// Housekeeping --------------------------------------------------------------------------------------------------------------
void clear() { Node* tmp{ head }; while (tmp) { Node* toDelete{ tmp }; tmp = tmp->next; delete toDelete; } head = nullptr; }
int empty() const { return head == nullptr; }
int size() const { int k{}; Node* n{ head }; while (n) { k; n = n->next; } return k; }
// Modify content --------------------------------------------------------------------------------------------------------------
void push_front(const T& i) { Node* n = new Node(i); n->next = head; head = n; };
void push_back(const T& i) { Node* n = new Node(i); Node* l = getLast(); if (l) l->next = n; else head = n; }
void pop_front() { if (head) { Node* tmp = head->next; delete head; head = tmp; } }
void pop_back() { // This is a little bit more difficult in a singly linked list
if (head) {
Node* n{ head }, * previous{};
while (n and n->next) {
previous = n;
n = n->next;
}
delete n;
if (previous)
previous->next = nullptr;
else
head->next = nullptr;
}
}
// Access elements --------------------------------------------------------------------------------
T& front() const { return head ? head->data : 0; };
T back() const { Node* n = getLast(); return n ? n->data : 0; }
// Add iterator properties to class ---------------------------------------------------------------
struct iterator { // Local class for iterator
Node* iter{}; // Iterator is basically a pointer to the node
Node* head{};
// Define alias names necessary for the iterator functionality
using iterator_category = std::bidirectional_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = T;
using pointer = T*;
using reference = T&;
// Constructor
iterator() {}
iterator(Node* n, Node* h) : iter(n), head(h) {}
// Dereferencing
reference operator *() const { return iter->data; }
pointer operator ->() const { return &iter->data; }
// Aithmetic operations
iterator& operator () { if (iter) iter = iter->next; return *this; }
iterator operator (int) { iterator temp{ *this }; * this; return temp; }
// Clumsy subtratcion
iterator& operator --() { Node* tmp = head; while (tmp and tmp->next != this->iter) tmp = tmp->next; iter = tmp; return *this; }
iterator operator --(int) { iterator temp{ *this }; --* this; return temp; }
iterator operator (const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--) temp; else while (k )--temp; return temp;
}
iterator operator =(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--) * this; else while (k )--* this; return *this;
};
iterator operator -(const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--)--temp; else while (k ) temp; return temp;
}
iterator operator -=(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--)--* this; else while (k ) * this; return *this;
};
// Comparison
bool operator != (const iterator& other) const { return iter != other.iter; }
bool operator == (const iterator& other) const { return iter == other.iter; }
bool operator < (const iterator& other) const { return iter < other.iter; }
bool operator > (const iterator& other) const { return iter > other.iter; }
bool operator <= (const iterator& other) const { return iter <= other.iter; }
bool operator >= (const iterator& other) const { return iter >= other.iter; }
// Difference. Also complicated, because no random access
difference_type operator-(const iterator& other) const {
difference_type result{};
Node* n{ iter };
while (n and n != other.iter) {
result;
n = n->next;
}
return result;
}
};
// Begin and end function to initialize an iterator
iterator begin() const { return iterator(head, head); }
iterator end() const { return iterator(nullptr, head); }
// Functions typcical for forward lists ----------------------------------------------------------------------
// Easy, becuase we can operate form the current iterator and do not need the "previous" element
iterator insertAfter(iterator& pos, const T& i) {
iterator result(nullptr, head);
if (pos.iter and pos.iter->next) {
Node* n = new Node(i, pos.iter->next);
pos.iter->next = n;
result.iter = n;
}
return result;
}
iterator eraseAfter(iterator& pos) {
iterator result(nullptr, head);
if (pos.iter and pos.iter->next) {
Node* tmp = pos.iter->next->next;
delete pos.iter->next;
pos.iter->next = tmp;
result.iter = pos.iter->next;
}
return result;
}
};
// Test/Driver Code
int main() {
// Example for initilizer list
SinglyLinkedList<int> sllbase{ 5,6,7,8,9,10,11,12,13,14,15 };
// Show move constructor
SinglyLinkedList<int> sll(std::move(sllbase));
// Add some values in the front
sll.push_front(4);
sll.push_front(3);
sll.push_front(2);
sll.push_front(1);
// Delete 1st element (Number 1)
sll.pop_front();
// Delete last element
sll.pop_back();
// Use a std::algorithm on our custom linked list. Works because we have an interator
SinglyLinkedList<int>::iterator iter = std::find(sll.begin(), sll.end(), 8);
iter;
--iter;
// Now add an element after 8
iter = sll.insertAfter(iter, 88);
// And delete the 9
iter = sll.eraseAfter(iter);
// Use range based for loop. Works because, we have iterators
for (int i : sll)
std::cout << i << ' ';
// Reverse Output
std::cout << "\n\n";
std::reverse_iterator<SinglyLinkedList<int>::iterator> riter = std::make_reverse_iterator(sll.end());
std::reverse_iterator<SinglyLinkedList<int>::iterator> riterEnd = std::make_reverse_iterator(sll.begin());
for (; riter != riterEnd; riter)
std::cout << *riter << ' ';
std::cout << "\n\n";
return 0;
}
Double linked list. Similar to std::list
#include <iostream>
#include <iterator>
#include <vector>
#include <type_traits>
#include <initializer_list>
#include <algorithm>
#include <list>
// ------------------------------------------------------------------------------------------------
// This would be in a header file -----------------------------------------------------------------
// Type trait helper to identify iterators --------------------------------------------------------
template<typename T, typename = void>
struct is_iterator { static constexpr bool value = false; };
template<typename T>
struct is_iterator<T, typename std::enable_if<!std::is_same<typename std::iterator_traits<T>::value_type, void>::value>::type> {
static constexpr bool value = true;
};
// The List class ---------------------------------------------------------------------------------
template <typename T>
class List {
// Sub class for a Node -----------
struct Node {
Node* next{};
Node* previous{};
T data{};
Node(Node* const n, Node* const p, const T& d) : next(n), previous(p), data(d) {}
Node(Node* const n, Node* const p) : next(n), previous(p) {}
Node() {}
};
// Private list data and functions --------
size_t numberOfElements{};
Node* head{};
void init() { head = new Node(); head->next = head; head->previous = head; numberOfElements = 0; }
public:
struct iterator; // Forward declaration
// Constructor --------------------
List() { init(); }
explicit List(const size_t count, const T& value) { init(); insert(begin(), count, value); };
explicit List(const size_t count) { init(); insert(begin(), count); }
template <typename Iter>
List(const Iter& first, const Iter& last) { init(); insert(begin(), first, last); }
List(const List& other) { init(), insert(begin(), other.begin(), other.end()); };
List(List&& other) : head(other.head), numberOfElements(other.numberOfElements) { other.init(); }
List(const std::initializer_list<T>& il) { init(); insert(begin(), il.begin(), il.end()); }
template <int N> List(const T(&other)[N]) { init(); insert(begin(), std::begin(other), std::end(other)); }
template <int N> List(T(&other)[N]) { init(); insert(begin(), std::begin(other), std::end(other)); }
// Assignment ---------------------
List& operator =(const List& other) { clear(); insert(begin(), other.begin(), other.end()); return *this; }
List& operator =(List&& other) { clear(); head = other.head; numberOfElements = other.numberOfElements; other.init(); return *this; }
List& operator =(const std::initializer_list<T>& il) { clear(); insert(begin(), il.begin(), il.end()); return *this; }
template <int N> List& operator =(const T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
template <int N> List& operator =(T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
void assign(const size_t count, const T& value) { clear(); insert(begin(), count, value); }
void assign(const std::initializer_list<T>& il) { clear(); insert(begin(), il.begin(), il.end()); }
template <typename Iter> void assign(const Iter& first, const Iter& last) { clear(); insert(begin(), first, last); }
template <int N> void assign(const T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
template <int N> void assign(T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
// Destructor ---------------------
~List() { clear(); }
// Element Access -----------------
T& front() { return *begin(); }
T& back() { return *(--end()); }
// Iterators ----------------------
iterator begin() const { return iterator(head->next, head); }
iterator end() const { return iterator(head, head); }
// Capacity -----------------------
size_t size() const { return numberOfElements; }
bool empty() { return size() == 0; }
// Modifiers ----------------------
void clear();
iterator insert(const iterator& insertBeforePosition, const T& value);
iterator insert(const iterator& insertBeforePosition);
template <class Iter, std::enable_if_t<is_iterator<Iter>::value, bool> = true>
iterator insert(const iterator& insertBeforePosition, const Iter& first, const Iter& last);
iterator insert(const iterator& insertBeforePosition, const size_t& count, const T& value);
iterator insert(const iterator& insertBeforePosition, const std::initializer_list<T>& il);
iterator erase(const iterator& posToDelete);
iterator erase(const iterator& first, const iterator& last);
void push_back(const T& d) { insert(end(), d); }
void pop_back() { erase(--end()); };
void push_front(const T& d) { insert(begin(), d); }
void pop_front() { erase(begin()); };
void resize(size_t count);
void resize(size_t count, const T& value);
void swap(List& other) { std::swap(head, other.head); std::swap(numberOfElements, other.numberOfElements); }
// Operations --------------------
void reverse();
// Non standard inefficient functions --------------------------
T& operator[](const size_t index) const { return begin()[index]; }
// ------------------------------------------------------------------------
// Define iterator capability ---------------------------------------------
struct iterator {
// Definitions ----------------
using iterator_category = std::bidirectional_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = T;
using pointer = T*;
using reference = T&;
// Data -----------------------
Node* iter{};
Node* head{};
// Constructor ----------------
iterator(Node* const node, Node* const h) : iter(node), head(h) {};
iterator() {};
// Dereferencing --------------
reference operator*() const { return iter->data; }
reference operator->() const { return &**this; }
// Arithmetic operations ------
iterator operator () { iter = iter->next; return *this; }
iterator operator (int) { iterator tmp = *this; * this; return tmp; }
iterator operator--() { iter = iter->previous; return *this; }
iterator operator--(int) { iterator tmp = *this; --* this; return tmp; }
iterator operator (const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--) temp; else while (k )--temp; return temp;
}
iterator operator =(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--) * this; else while (k )--* this; return *this;
};
iterator operator -(const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--)--temp; else while (k ) temp; return temp;
}
iterator operator -=(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--)--* this; else while (k ) * this; return *this;
};
// Comparison ----------------- (typical space ship implementation)
bool operator ==(const iterator& other) const { return iter == other.iter; };
bool operator !=(const iterator& other) const { return iter != other.iter; };
bool operator < (const iterator& other) const { return other.iter - iter < 0; };
bool operator <= (const iterator& other) const { return other.iter - iter <= 0; };
bool operator > (const iterator& other) const { return other.iter - iter > 0; };
bool operator >= (const iterator& other) const { return other.iter - iter >= 0; };
// Special non standard functions -----------------
difference_type operator-(const iterator& other) const;
reference operator[] (const size_t index);
};
};
// ------------------------------------------------------------------------------------------------
// Implementation of list functions. This would normally go into a TCC file -----------------------
// List class functions ---------------
template <typename T>
void List<T>::clear() {
for (Node* nextNode{}, * currentNode(head->next); currentNode != head; currentNode = nextNode) {
nextNode = currentNode->next;
delete currentNode;
}
init();
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const T& value)
{
Node* nodeInsertBeforePosition = insertBeforePosition.iter;
Node* newNode = new Node(nodeInsertBeforePosition, nodeInsertBeforePosition->previous, value);
nodeInsertBeforePosition->previous = newNode;
(newNode->previous)->next = newNode;
numberOfElements;
return iterator(newNode, head);
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition)
{
Node* nodeInsertBeforePosition = insertBeforePosition.iter;
Node* newNode = new Node(nodeInsertBeforePosition, nodeInsertBeforePosition->previous);
nodeInsertBeforePosition->previous = newNode;
(newNode->previous)->next = newNode;
numberOfElements;
return iterator(newNode, head);
}
template <typename T>
template <class Iter, std::enable_if_t<is_iterator<Iter>::value, bool>>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const Iter& first, const Iter& last) {
iterator result(insertBeforePosition.iter, head);
if (first != last) {
result = insert(insertBeforePosition, *first);
Iter i(first);
for ( i; i != last; i)
insert(insertBeforePosition, *i);
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const size_t& count, const T& value) {
iterator result(insertBeforePosition.iter, head);
if (count != 0u) {
result = insert(insertBeforePosition, value);
for (size_t i{ 1u }; i < count; i)
insert(insertBeforePosition, value);
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const std::initializer_list<T>& il) {
return insert(insertBeforePosition, il.begin(), il.end());
}
template <typename T>
typename List<T>::iterator List<T>::erase(const List<T>::iterator& posToDelete) {
iterator result = posToDelete;
result;
Node* nodeToDelete = posToDelete.iter;
if (nodeToDelete != head) {
nodeToDelete->previous->next = nodeToDelete->next;
nodeToDelete->next->previous = nodeToDelete->previous;
delete nodeToDelete;
--numberOfElements;
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::erase(const List<T>::iterator& first, const List<T>::iterator& last) {
iterator result{ end() };
if (first == begin() && last == end())
clear();
else {
while (first != last)
first = erase(first);
result = last;
}
return result;
}
template <typename T>
void List<T>::resize(size_t count) {
if (numberOfElements < count)
for (size_t i{ numberOfElements }; i < count; i)
insert(end());
else
while (count--)
pop_back();
}
template <typename T>
void List<T>::resize(size_t count, const T& value) {
if (numberOfElements < count)
for (size_t i{ numberOfElements }; i < count; i)
insert(end(), value);
else
while (count--)
pop_back();
}
template <typename T>
void List<T>::reverse() {
const Node* oldHead = head;
for (Node* nptr = head; ; nptr = nptr->previous) {
std::swap(nptr->next, nptr->previous);
if (nptr->previous == oldHead) // Previous was the original next
break;
}
}
// ------------------------------------
// Iterator functions -----------------
template <typename T>
typename List<T>::iterator::difference_type List<T>::iterator::operator-(const iterator& other) const {
difference_type result{};
Node* nptr = head;
int indexThis{ -1 }, indexOther{ -1 }, index{};
do {
nptr = nptr->next;
if (nptr == iter)
indexThis = index;
if (nptr == other.iter)
indexOther = index;
index;
} while (nptr != head);
if (indexThis >= 0 and indexOther >= 0)
result = indexThis - indexOther;
return result;
}
template <typename T>
typename List<T>::iterator::reference List<T>::iterator::operator[] (const size_t index) {
Node* nptr = head->next;
for (size_t i{}; i < index and nptr != head; i, nptr = nptr->next)
;
return nptr->data;
}
// ------------------------------------------------------------------------------------------------
// This would be in a cpp file --------------------------------------------------------------------
int main() {
List<int> list3{ 10,20 };
List<int>::iterator l3 = list3.end();
for (int k = 0; k < 10; k) {
std::cout << *l3 << ' ';
--l3;
}
std::cout << '\n';
// Custom list
List<int> list2{ 1, 2, 3, 4, 5 };
for (int i : list2)
std::cout << i << ' '; std::cout << '\n';
// Delta works
std::cout << list2.begin() - list2.end() << '\n';
std::cout << list2.end() - list2.begin() << '\n';
// Hopp Count works
List<int>::iterator i = list2.end();
while (i-- != list2.begin())
std::cout << *i << ' '; std::cout << '\n';
}
CodePudding user response：
I think the errors that you get, are of course resulting from some wrong coding implementation. And those have been corrected already in other answers.
But for me the biggest problem is the wrong design.
Obviously you are mixing up "Node" with the "linked list". In real world applications the "Node" is a part of a linked list. In object oriented language we have a "has a" relation. So, a linked list has a Node.
Additionally, the whole "Node" functionality would be encapsulated in the linked list. So, the "Node" would NOT be visible to the outside world.
If we interact with a linked list to store or retrive values and such, we would never know about (and even not be interested in) the internas like a "Node".
And, maybe because of that suboptimal design approach, you will create errors.
So, maybe it would be a good idea to refactor your design, and after that, implement it in some better way. For example, use classes, no global avariables and no free functions to operate on list data.
To give you an idea on what could be done, I will show you some implementation of a singly linked list and a double linked list.
Single Linked List:
#include <iterator>
#include <algorithm>
#include <iostream>
#include <initializer_list>
// Very simple implementation of a forward list
template <class T>
class SinglyLinkedList {
// The node
struct Node {
T data{}; // Data. Would normally be a templated argument
Node* next{}; // And the pointer to the next node
Node(const T& i, Node* n = nullptr) : data(i), next(n) {}; // Simple constructor to set a value and next pointer
};
Node* head{}; // This is the start of the list
// It would be advisable to have a tail pointer. We use the more inefficient approach here
Node* getLast() const { Node* n{ head }; while (n and n->next) n = n->next; return n; }
public:
// Constructor / Destructor --------------------------------------------------------------------------------------------------------
~SinglyLinkedList() { clear(); }
// Default constuctor
SinglyLinkedList() {} // Default
// From an initialization list
SinglyLinkedList(const std::initializer_list<T>& il) { clear(); for (const T& i : il) push_back(i); } // From initializer list
// Copy constructor
SinglyLinkedList(const SinglyLinkedList& other) { clear(); for (const T& i : other) push_back(i); }
// Move constructor. Will steal the elements from the other
SinglyLinkedList(SinglyLinkedList&& other) noexcept { head = other.head; other.head = nullptr; }
// Assignment operator
SinglyLinkedList& operator = (const SinglyLinkedList& other) { clear(); for (const T& i : other) push_back(i); }
// Move assignment operator
SinglyLinkedList& operator = (SinglyLinkedList&& other) { head = other.head; other.head = nullptr; }
// Housekeeping --------------------------------------------------------------------------------------------------------------
void clear() { Node* tmp{ head }; while (tmp) { Node* toDelete{ tmp }; tmp = tmp->next; delete toDelete; } head = nullptr; }
int empty() const { return head == nullptr; }
int size() const { int k{}; Node* n{ head }; while (n) { k; n = n->next; } return k; }
// Modify content --------------------------------------------------------------------------------------------------------------
void push_back(const T& i) { Node* n = new Node(i); Node* l = getLast(); if (l) l->next = n; else head = n; }
void push_front(const T& i) { Node* n = new Node(i); n->next = head; head = n; };
void pop_back() { // This is a little bit more difficult in a singly linked list
if (head) {
Node* n{ head }, * previous{};
while (n and n->next) {
previous = n;
n = n->next;
}
delete n;
if (previous)
previous->next = nullptr;
else
head->next = nullptr;
}
}
void pop_front() { if (head) { Node* tmp = head->next; delete head; head = tmp; } }
// Access elements --------------------------------------------------------------------------------
T back() const { Node* n = getLast(); return n ? n->data : 0; }
T front() const { return head ? head->data : 0; };
// Add iterator properties to class ---------------------------------------------------------------
struct iterator { // Local class for iterator
Node* iter{}; // Iterator is basically a pointer to the node
Node* head{};
// Define alias names necessary for the iterator functionality
using iterator_category = std::bidirectional_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = T;
using pointer = T*;
using reference = T&;
// Constructor
iterator() {}
iterator(Node* n, Node* h) : iter(n), head(h) {}
// Dereferencing
reference operator *() const { return iter->data; }
pointer operator ->() const { return &iter->data; }
// Aithmetic operations
iterator& operator () { if (iter) iter = iter->next; return *this; }
iterator& operator --() { Node* tmp = head; while (tmp and tmp->next != this->iter) tmp = tmp->next; iter = tmp; return *this; }
iterator operator (int) { iterator temp{ *this }; * this; return temp; }
iterator operator --(int) { iterator temp{ *this }; --* this; return temp; }
iterator operator (const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--) temp; else while (k )--temp; return temp; }
iterator operator =(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--) * this; else while (k )--* this; return *this; };
iterator operator -(const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--)--temp; else while (k ) temp; return temp; }
iterator operator -=(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--)--* this; else while (k ) * this; return *this; };
// Comparison
bool operator != (const iterator& other) const { return iter != other.iter; }
bool operator == (const iterator& other) const { return iter == other.iter; }
bool operator < (const iterator& other) const { return iter < other.iter; }
bool operator <= (const iterator& other) const { return iter <= other.iter; }
bool operator > (const iterator& other) const { return iter > other.iter; }
bool operator >= (const iterator& other) const { return iter >= other.iter; }
// Difference. Also complicated, because no random access
difference_type operator-(const iterator& other) const {
difference_type result{};
Node* n{ iter };
while (n and n != other.iter) {
result;
n = n->next;
}
return result;
}
};
// Begin and end function to initialize an iterator
iterator begin() const { return iterator(head, head); }
iterator end() const { return iterator(nullptr, head); }
// Functions typcical for forward lists ----------------------------------------------------------------------
// Easy, becuase we can operate form the current iterator and do not need the "previous" element
iterator insertAfter(iterator& pos, const T& i) {
iterator result(nullptr, head);
if (pos.iter and pos.iter->next) {
Node* n = new Node(i, pos.iter->next);
pos.iter->next = n;
result.iter = n;
}
return result;
}
iterator eraseAfter(iterator& pos) {
iterator result(nullptr, head);
if (pos.iter and pos.iter->next) {
Node* tmp = pos.iter->next->next;
delete pos.iter->next;
pos.iter->next = tmp;
result.iter = pos.iter->next;
}
return result;
}
};
// Test/Driver Code
int main() {
// Example for initilizer list
SinglyLinkedList<int> sllbase{ 5,6,7,8,9,10,11,12,13,14,15 };
// Show move constructor
SinglyLinkedList<int> sll(std::move(sllbase));
// Add some values in the front
sll.push_front(4);
sll.push_front(3);
sll.push_front(2);
sll.push_front(1);
// Delete 1st element (Number 1)
sll.pop_front();
// Delete last element
sll.pop_back();
// Use a std::algorithm on our custom linked list. Works because we have an interator
SinglyLinkedList<int>::iterator iter = std::find(sll.begin(), sll.end(), 8);
iter;
--iter;
// Now add an element after 8
iter = sll.insertAfter(iter, 88);
// And delete the 9
iter = sll.eraseAfter(iter);
// Use range based for loop. Works because, we have iterators
for (int i : sll)
std::cout << i << ' ';
// Reverse Output
std::cout << "\n\n";
std::reverse_iterator<SinglyLinkedList<int>::iterator> riter = std::make_reverse_iterator(sll.end());
std::reverse_iterator<SinglyLinkedList<int>::iterator> riterEnd = std::make_reverse_iterator(sll.begin());
for (; riter != riterEnd; riter)
std::cout << *riter << ' ';
std::cout << "\n\n";
return 0;
}
// Chekcsum
// HazccLR7ffCWA2vBnboBukO3nANVi0KDUi9giVk6jznSZ1fiCUcGCXUEAjyxAN2jT6SEeL28kKdRBnUUh5ztainlpXoLhUKcwGay
// wbfid3BnBBDF7gzh0y7jzY71eVS5zAH1C4rWugWQ8vbhpWL1AtOdAj2PNrwVwUIDVSvuuDHAMW2yQYQfFjZubFYnmJkkqoaP9XCE
Double linked list. Similar to std::list
#include <iterator>
#include <initializer_list>
#include <algorithm>
#include <iostream>
#include <type_traits>
#include <vector>
// ------------------------------------------------------------------------------------------------
// This would be in a header file -----------------------------------------------------------------
// Type trait helper to identify iterators --------------------------------------------------------
template<typename T, typename = void>
struct is_iterator { static constexpr bool value = false; };
template<typename T>
struct is_iterator<T, typename std::enable_if<!std::is_same<typename std::iterator_traits<T>::value_type, void>::value>::type> {
static constexpr bool value = true;
};
// The List class ---------------------------------------------------------------------------------
template <typename T>
class List {
// Sub class for a Node -----------
struct Node {
T data{};
Node* next{};
Node* previous{};
Node() {}
Node(Node* const n, Node* const p) : next(n), previous(p) {}
Node(Node* const n, Node* const p, const T& d) : next(n), previous(p), data(d) {}
};
// Private list data and functions --------
Node* head{};
size_t numberOfElements{};
void init() { head = new Node(); head->next = head; head->previous = head; numberOfElements = 0; }
public:
struct iterator; // Forward declaration
// Constructor --------------------
List() { init(); }
explicit List(const size_t count) { init(); insert(begin(), count); }
explicit List(const size_t count, const T& value) { init(); insert(begin(), count, value); };
template <typename Iter>
List(const Iter& first, const Iter& last) { init(); insert(begin(), first, last); }
List(const List& other) { init(), insert(begin(), other.begin(), other.end()); };
List(List&& other) : head(other.head), numberOfElements(other.numberOfElements) { other.init(); }
List(const std::initializer_list<T>& il) { init(); insert(begin(), il.begin(), il.end()); }
template <int N> List(T(&other)[N]) { init(); insert(begin(), std::begin(other), std::end(other)); }
template <int N> List(const T(&other)[N]) { init(); insert(begin(), std::begin(other), std::end(other)); }
// Assignment ---------------------
List& operator =(const List& other) { clear(); insert(begin(), other.begin(), other.end()); return *this; }
List& operator =(List&& other) { clear(); head = other.head; numberOfElements = other.numberOfElements; other.init(); return *this; }
List& operator =(const std::initializer_list<T>& il) { clear(); insert(begin(), il.begin(), il.end()); return *this; }
template <int N> List& operator =(const T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
template <int N> List& operator =(T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
template <typename Iter> void assign(const Iter& first, const Iter& last) { clear(); insert(begin(), first, last); }
template <int N> void assign(const T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
template <int N> void assign(T(&other)[N]) { clear(); insert(begin(), std::begin(other), std::end(other)); return *this; }
void assign(const size_t count, const T& value) { clear(); insert(begin(), count, value); }
void assign(const std::initializer_list<T>& il) { clear(); insert(begin(), il.begin(), il.end()); }
// Destructor ---------------------
~List() { clear(); }
// Element Access -----------------
T& front() { return *begin(); }
T& back() { return *(--end()); }
// Iterators ----------------------
iterator begin() const { return iterator(head->next, head); }
iterator end() const { return iterator(head, head); }
// Capacity -----------------------
size_t size() const { return numberOfElements; }
bool empty() { return size() == 0; }
// Modifiers ----------------------
void clear();
iterator insert(const iterator& insertBeforePosition, const T& value);
iterator insert(const iterator& insertBeforePosition);
template <class Iter, std::enable_if_t<is_iterator<Iter>::value, bool> = true>
iterator insert(const iterator& insertBeforePosition, const Iter& first, const Iter& last);
iterator insert(const iterator& insertBeforePosition, const size_t& count, const T& value);
iterator insert(const iterator& insertBeforePosition, const std::initializer_list<T>& il);
iterator erase(const iterator& posToDelete);
iterator erase(const iterator& first, const iterator& last);
void pop_front() { erase(begin()); };
void push_front(const T& d) { insert(begin(), d); }
void pop_back() { erase(--end()); };
void push_back(const T& d) { insert(end(), d); }
void resize(size_t count, const T& value);
void resize(size_t count);
void swap(List& other) { std::swap(head, other.head); std::swap(numberOfElements, other.numberOfElements); }
// Operations --------------------
void reverse();
// Non standard inefficient functions --------------------------
T& operator[](const size_t index) const { return begin()[index]; }
// ------------------------------------------------------------------------
// Define iterator capability ---------------------------------------------
struct iterator {
// Definitions ----------------
using iterator_category = std::bidirectional_iterator_tag;
using difference_type = std::ptrdiff_t;
using value_type = T;
using pointer = T*;
using reference = T&;
// Data -----------------------
Node* iter{};
Node* head{};
// Constructor ----------------
iterator(Node* const node, Node* const h) : iter(node), head(h) {};
iterator() {};
// Dereferencing --------------
reference operator*() const { return iter->data; }
reference operator->() const { return &**this; }
// Arithmetic operations ------
iterator operator () { iter = iter->next; return *this; }
iterator operator--() { iter = iter->previous; return *this; }
iterator operator (int) { iterator tmp = *this; * this; return tmp; }
iterator operator--(int) { iterator tmp = *this; --* this; return tmp; }
iterator operator (const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--) temp; else while (k )--temp; return temp;
}
iterator operator =(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--) * this; else while (k )--* this; return *this;
};
iterator operator -(const difference_type& n) const {
iterator temp{ *this }; difference_type k{ n }; if (k > 0) while (k--)--temp; else while (k ) temp; return temp;
}
iterator operator -=(const difference_type& n) {
difference_type k{ n }; if (k > 0) while (k--)--* this; else while (k ) * this; return *this;
};
// Comparison ----------------- (typical space ship implementation)
bool operator ==(const iterator& other) const { return iter == other.iter; };
bool operator !=(const iterator& other) const { return iter != other.iter; };
bool operator < (const iterator& other) const { return other.iter - iter < 0; };
bool operator <= (const iterator& other) const { return other.iter - iter <= 0; };
bool operator > (const iterator& other) const { return other.iter - iter > 0; };
bool operator >= (const iterator& other) const { return other.iter - iter >= 0; };
// Special non standard functions -----------------
difference_type operator-(const iterator& other) const;
reference operator[] (const size_t index);
};
};
// ------------------------------------------------------------------------------------------------
// Implementation of list functions. This would normally go into a TCC file -----------------------
// List class functions ---------------
template <typename T>
void List<T>::clear() {
for (Node* nextNode{}, * currentNode(head->next); currentNode != head; currentNode = nextNode) {
nextNode = currentNode->next;
delete currentNode;
}
init();
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const T& value)
{
Node* nodeInsertBeforePosition = insertBeforePosition.iter;
Node* newNode = new Node(nodeInsertBeforePosition, nodeInsertBeforePosition->previous, value);
nodeInsertBeforePosition->previous = newNode;
(newNode->previous)->next = newNode;
numberOfElements;
return iterator(newNode, head);
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition)
{
Node* nodeInsertBeforePosition = insertBeforePosition.iter;
Node* newNode = new Node(nodeInsertBeforePosition, nodeInsertBeforePosition->previous);
nodeInsertBeforePosition->previous = newNode;
(newNode->previous)->next = newNode;
numberOfElements;
return iterator(newNode, head);
}
template <typename T>
template <class Iter, std::enable_if_t<is_iterator<Iter>::value, bool>>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const Iter& first, const Iter& last) {
iterator result(insertBeforePosition.iter, head);
if (first != last) {
result = insert(insertBeforePosition, *first);
Iter i(first);
for ( i; i != last; i)
insert(insertBeforePosition, *i);
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const size_t& count, const T& value) {
iterator result(insertBeforePosition.iter, head);
if (count != 0u) {
result = insert(insertBeforePosition, value);
for (size_t i{ 1u }; i < count; i)
insert(insertBeforePosition, value);
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::insert(const List<T>::iterator& insertBeforePosition, const std::initializer_list<T>& il) {
return insert(insertBeforePosition, il.begin(), il.end());
}
template <typename T>
typename List<T>::iterator List<T>::erase(const List<T>::iterator& posToDelete) {
iterator result = posToDelete;
result;
Node* nodeToDelete = posToDelete.iter;
if (nodeToDelete != head) {
nodeToDelete->previous->next = nodeToDelete->next;
nodeToDelete->next->previous = nodeToDelete->previous;
delete nodeToDelete;
--numberOfElements;
}
return result;
}
template <typename T>
typename List<T>::iterator List<T>::erase(const List<T>::iterator& first, const List<T>::iterator& last) {
iterator result{ end() };
if (first == begin() && last == end())
clear();
else {
while (first != last)
first = erase(first);
result = last;
}
return result;
}
template <typename T>
void List<T>::resize(size_t count) {
if (numberOfElements < count)
for (size_t i{ numberOfElements }; i < count; i)
insert(end());
else
while (count--)
pop_back();
}
template <typename T>
void List<T>::resize(size_t count, const T& value) {
if (numberOfElements < count)
for (size_t i{ numberOfElements }; i < count; i)
insert(end(), value);
else
while (count--)
pop_back();
}
template <typename T>
void List<T>::reverse() {
const Node* oldHead = head;
for (Node* nptr = head; ; nptr = nptr->previous) {
std::swap(nptr->next, nptr->previous);
if (nptr->previous == oldHead) // Previous was the original next
break;
}
}
// ------------------------------------
// Iterator functions -----------------
template <typename T>
typename List<T>::iterator::difference_type List<T>::iterator::operator-(const iterator& other) const {
difference_type result{};
Node* nptr = head;
int indexThis{ -1 }, indexOther{ -1 }, index{};
do {
nptr = nptr->next;
if (nptr == iter)
indexThis = index;
if (nptr == other.iter)
indexOther = index;
index;
} while (nptr != head);
if (indexThis >= 0 and indexOther >= 0)
result = indexThis - indexOther;
return result;
}
template <typename T>
typename List<T>::iterator::reference List<T>::iterator::operator[] (const size_t index) {
Node* nptr = head->next;
for (size_t i{}; i < index and nptr != head; i, nptr = nptr->next)
;
return nptr->data;
}
// ------------------------------------------------------------------------------------------------
// This would be in a cpp file --------------------------------------------------------------------
int main() {
List<int> list3{ 10,20 };
List<int>::iterator l3 = list3.end();
for (int k = 0; k < 10; k) {
std::cout << *l3 << ' ';
--l3;
}
std::cout << '\n';
// Custom list
List<int> list2{ 1, 2, 3, 4, 5 };
for (int i : list2)
std::cout << i << ' '; std::cout << '\n';
// Delta works
std::cout << list2.begin() - list2.end() << '\n';
std::cout << list2.end() - list2.begin() << '\n';
// Hopp Count works
List<int>::iterator i = list2.end();
while (i-- != list2.begin())
std::cout << *i << ' '; std::cout << '\n';
}
// Checksums
// W0CqlMhAO8nfQD9IniOhkyEGCnFicc6wpyL3Q03wwz0pgJDrm8DNKRrykxDAiamOs99F66EaDzeeLoq0m3jiHEp1HVgOqoymxM3Q
// AUnIVeK4ER9gyM4qMBU2cZGS0PK6ZKzuhEFCuwbu7UYRBoy4HOdTZ2dclLnUd7fX2uUOUzzdNZluoRCtOatyAgpjqYPMxG02o95j