I have to code a program where I have to delete specific letters from a text string.

For example, if the user types in text like "Hepello Ipe hapeve ape prpeobpelepem", the code has to automatically delete the 'pe' letters so the text becomes the normal "Hello I have a problem".

I tried to program this with the list functions, but my teacher said that I HAVE to use pointers and dynamic structures, which I suck at.

Can someone help me?

Here is what I have so far. My 2nd code is still pretty empty:

#include <iostream>
#include <string>
#include <list>

using namespace std;

list<string> createCodeList()
{
    list<string> codeList;
    string input;

    cout << "Enter your coded text: " << endl;
    getline(cin, input);
   
    for (int i = 0; i < input.length(); i  = 3)
    {
        string code = input.substr(i, 2);
        codeList.push_back(code);
    }

    return codeList;
}

void removeCodeWords(list<string>& codeList)
{
    for (auto it = codeList.begin(); it != codeList.end(); )
    {
        if (*it == "pe")
        {
            it = codeList.erase(it);
        }
        else
        {
              it;
        }
    }
}

void printCodeList(const list<string>& codeList)
{
    for (const string& code : codeList)
    {
        cout << code;
    }
    cout << endl;
}

int main()
{
    list<string> codeList = createCodeList();
    removeCodeWords(codeList);
    printCodeList(codeList);
    return 0;
}

#include <iostream>
#include <string>

using namespace std;

struct Codedtext
{
    string text;    
};

typedef Codedtext* point;

point Createlist()
{
    point list = NULL;
    char input;
    cout << "Enter your coded text: " << endl;
    cin >> input;
}

int main()
{
    return 0;
}

CodePudding user response：

Your std::list code doesn't work because your createCodeList() function is not breaking up the user's input correctly. It is extracting 2 characters from every group of 3 characters, regardless of where the "pe" substrings are actually located (hint: they are NOT located at even intervals of 3 characters).

IOW, you are breaking up the input like this:

Hep|ell|o I|pe |hap|eve| ap|e p|rpe|obp|ele|pem

Hep -> He
ell -> el
o I -> o
pe -> pe (removed)
hap -> ha
eve -> ev
ap -> a
e p -> e
rpe -> rp
obp -> ob
ele -> el
pem -> pe (removed)

So your output ends up as:

Heelo haev ae rpobel

Whereas the correct breakup would look like this instead (note the groupings are NOT the same length):

He|pe|llo I|pe| ha|pe|ve a|pe| pr|pe|ob|pe|le|pe|m

He
pe (removed)
llo I
pe (removed)
ha
pe (removed)
ve a
pe (removed)
pr
pe (removed)
ob
pe (removed)
le
pe (removed)
m

So the output would be:

Hello I have a problem

See the difference?

With that said, try this instead:

list<string> createCodeList()
{
    list<string> codeList;
    string input;

    cout << "Enter your coded text: " << endl;
    getline(cin, input);
   
    string::size_type start = 0, end;
    while ((end = input.find("pe", start)) != string::npos)
    {
        codeList.push_back(input.substr(start, end-start));
        codeList.push_back("pe");
        start = end   2;
    }
    if (start < input.size())
        codeList.push_back(input.substr(start));

    return codeList;
}

Now the rest of your code will work as expected.

Online Demo

That being said, since your teacher doesn't want you to use std::list, you could simply implement the linked-list yourself, something like this:

#include <iostream>
#include <string>

using namespace std;

struct Codedtext
{
    string text;
    Codedtext* next = nullptr;
};

using CodedtextPtr = Codedtext*;

CodedtextPtr createCodeList()
{
    CodedtextPtr codeList = nullptr;
    CodedtextPtr *node = &codeList;
    string input;

    cout << "Enter your coded text: " << endl;
    getline(cin, input);
   
    string::size_type start = 0, end;
    while ((end = input.find("pe", start)) != string::npos)
    {
        *node = new Codedtext{ input.substr(start, end-start) };
        node = &((*node)->next);

        *node = new Codedtext{ "pe" };
        node = &((*node)->next);

        start = end   2;
    }
    if (start < input.size())
        *node = new Codedtext{ input.substr(start) };

    return codeList;
}

void removeCodeWords(CodedtextPtr& codeList)
{
    CodedtextPtr* previous = &codeList;
    
    for(auto it = codeList; it != nullptr; )
    {
        CodedtextPtr next = it->next;

        if (it->text == "pe")
        {
            *previous = next;
            delete it;
        }
        else
            previous = &(it->next);

        it = next;
    }
}

void printCodeList(CodedtextPtr codeList)
{
    while (codeList)
    {
        cout << codeList->text;
        codeList = codeList->next;
    }
    cout << endl;
}

void freeCodeList(CodedtextPtr codeList)
{
    while (codeList)
    {
        CodedtextPtr next = codeList->next;
        delete codeList;
        codeList = next;
    }
}

int main()
{
    CodedtextPtr codeList = createCodeList();
    removeCodeWords(codeList);
    printCodeList(codeList);
    freeCodeList(codeList);
    return 0;
}

Online Demo