Be urgent! Help your child see, why p is null-CodePudding

Help to take a look at why shows an uninitialized variable list: : head
Said P is null

# include
using namespace std;

Enum myerror_code {success, overflow, underflow, rangeerror};

Struct node
{
int data;
Node * next;
};
The class list
{
Public:
The list ();
Myerror_code insert (const int I, const int x);
The node * gethead () const;
Void the show () the const;
Private:
Int count;
Node * head;
};
The list: a list ()
{
The head node *=new node;
The head - & gt; Next=NULL;
count=0;
}
Myerror_code list: : insert (const int I, const int x)
{
Node * p=new node;
P=the head;
int j=0;
While (j!=I - 1 & amp; & p!=NULL)
{
P=p - & gt; Next;
j++;
}
If (p==NULL) return rangeerror;
Node * s=new node;
S - & gt; Data=https://bbs.csdn.net/topics/x;
S - & gt; Next=NULL;
S - & gt; Next=p - & gt; Next;
P - & gt; Next=s;
count++;
The return success.
}

CodePudding user response:

Reference:

 # include 
using namespace std; 

Enum myerror_code {success, overflow, underflow, rangeerror}; 

Struct node 
{
The int data; 
Node * next; 
}; 
The class list 
{
Public: 
The list (); 
Myerror_code insert (const int I, const int x); 
Const struct node * gethead (); 
Void the show () the const; 
Private: 
Int count; 
Struct node * head; 
}; 
The list: a list () 
{
The head=new node; 
The head - & gt; Data=https://bbs.csdn.net/topics/-1; 
The head - & gt; Next=NULL; 
count=0; 
} 
Myerror_code list: : insert (const int I, const int x) 
{
Struct node * p; 
P=the head; 
If (p==NULL) return rangeerror; 
int j=0; 
While (j!=I - 1 & amp; & P - & gt; Next!=NULL) 
{
P=p - & gt; Next; 
j++; 
} 
Struct node * s=new node; 
S - & gt; Data=https://bbs.csdn.net/topics/x; 
S - & gt; Next=NULL; 
S - & gt; Next=p - & gt; Next; 
P - & gt; Next=s; 
count++; 
The return success. 
} 
Void list: : show () const 
{
Struct node * p; 
P=the head - & gt; Next; 
While (p) {
Cout CodePudding user response: 
Fixed: line 24, line 40:  head=new struct node; 
  struct node * s=new struct node;