#std::string

20 messages · Page 1 of 1 (latest)

normal mountain
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Hey, I am a beginner in C++ and I don't really understand how to do my "homework". I'm asked to recreate std::string size, length, resize ect. Thing is that, I don't really understand how to do it. I'm aware that CPP reference explain how the func works, but I still don't understand how to do it by myself.

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static trellisBOT
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@normal mountain

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normal agate
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@normal mountain you have a char array, right?

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if you have a char array you can to calc the length/size of the string just go through every char and add 1 to an int per char.

normal mountain
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sorry for the late answer, I finished my code

#include "ministring.h"

Ministring::Ministring() {}

int Ministring::size()const
{
    return m_length;
}

int Ministring::length() const
{
    return m_length;
}

void Ministring::resize (int n){
    if (n < m_length){
        m_length = n;
        if (n>=0){
            m_str[n] = '\0';
        }
    }else if (n > m_length){
        char *new_str = new char[n+1];
        if (m_str != nullptr) {
            for (int i = 0; i < m_length; ++i) {
                new_str[i] = m_str[i];
            }
            delete[] m_str;
        }
        m_str = new_str;
        m_length = n;
    }
}
# 
#ifndef MINISTRING_MINISTRING_H
#define MINISTRING_MINISTRING_H

using namespace std;

#include <iostream>

class Ministring {

public:
    Ministring();
    int size() const;
    int length() const;
    void resize (int n);

private:
    char *m_str;
    int m_length;
};


#endif //MINISTRING_MINISTRING_H
normal mountain
normal agate
#

ok, what functions do you need to implement

normal mountain
#

I've to recreate all those =>

size

  • length
  • resize
  • clear
  • empty
  • at
  • insert
  • replace
  • find
  • substr

from the std::string

#

basically i've done

# 
using namespace std;

#include <iostream>

class Ministring {

public:
    Ministring();
    int size() const;
    int length() const;
    void resize (int n);
    void clear();
    bool empty() const;

private:
    char *m_str;
    int m_length;
};
# 
#include "ministring.h"

Ministring::Ministring() {}

int Ministring::size()const
{
    return m_length;
}

int Ministring::length() const
{
    return m_length;
}

void Ministring::resize (int n){
    if (n < m_length){
        m_length = n;
        if (n>=0){
            m_str[n] = '\0';
        }
    }else if (n > m_length){
        char *new_str = new char[n+1];
        if (m_str != nullptr) {
            for (int i = 0; i < m_length; ++i) {
                new_str[i] = m_str[i];
            }
            delete[] m_str;
        }
        m_str = new_str;
        m_length = n;
    }
}

void Ministring::clear(){
    if (m_length > 0){
        delete[] m_str;
        m_str = nullptr;
        m_length = 0;
    }
}

bool Ministring::empty() const
{
    if (m_length == 0){
        return true;
    }
    return false;
}
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But for empty, can't I just do "return (m_length = 0)" ?

normal agate
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replace is pretty essy, just go through the array like in length and replace any chars that are like the input with some other things

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i think just return (size() == 0), yeah

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find is also like replace and length, just go through the array and if you find the char return the index i think

normal mountain
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Alright, imma try. thaanks for the advices

normal agate
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yeah, the problem is i am not that good myself with char* and char[]

normal mountain
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Oh, don't worry, you tried and i'm good with that