How I can delete specific letters from a string of text?

Question

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;
}

Answer 1

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|ep|rpe|obp|ele|pem

Hep -> He
ell -> el
o I -> o
pe -> pe (removed)
hap -> ha
eve -> ev
ap -> a
ep -> 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