I need to solve this task using library string functions and without them.

I solved without special functions:

void without_functions(string str)
{
    int* how_many_num = new int[10];
    for (int i = 0; i < 10;   i)
        how_many_num[i] = 0;

    for (int i = 0; i < str.size();   i)
    {
        if (str[i] >= '0' && str[i] <= '9')
        {
              how_many_num[int(str[i]) - 48];
        }
    }

    for (int i = 0; i <= 9;   i)
    {
        if (how_many_num[i] != 0)
        {
            cout << "Digit " << i << " is founded" << how_many_num[i] << " times" << endl;
        }
    }
   
    for (int i = 0; i < str.size();   i)
    {
        if ((int(str[i]) >= 65 && int(str[i]) <= 90) || (int(str[i]) >= 97 && str[i] <= '122'))
        {
            str[i] = ' ';
        }
    }

    cout << endl << "New string:  " << str << endl;
}

I cannot come up with how to implement this task with string functions (methods).

CodePudding user response：

Welcome to Stackoverflow!

Some users might find it confusing when using phrasing "using library string functions". I only assume you meant standard library functions.

There are couple of ways to achieve this:

1. std::replace_ifand std::isdigit
2. regex replace
3. The newer ranges replace
4. You can also use string direct replace function - but I don't recommend it for this kind of exercise.

Choose your favorite, I'd recommend learning all of them :) Best of luck!

CodePudding user response：

There are a number of problems with without_functions():

• it is leaking how_many_num. You need to delete[] it when done using it. Better to use std::vector instead, but for such a small array, there is no point in using dynamic memory, just use a fixed array instead

• your cout loop is not allowing for 0 digits. You should fill the array elements with an initial value other than 0..9, and then look for that value instead of 0.

• your replacement loop is looking for '122' when it should be looking for 122 instead. However, you really should be using character literals instead of numeric ASCII codes. It is a bad habit to use magic numbers in coding.

• your loops to count digits and replace letters can be combined into a single loop.

Now, try something more like this:

void without_functions(string str)
{
    int how_many_num[10];
    for (int i = 0; i < 10;   i)
        how_many_num[i] = -1;

    for (size_t i = 0; i < str.size();   i)
    {
        if (str[i] >= '0' && str[i] <= '9')
        {
              how_many_num[str[i] - '0'];
        }
        else if ((str[i] >= 'A' && str[i] <= 'Z') || (str[i] >= 'a' && str[i] <= 'z'))
        {
            str[i] = ' ';
        }
    }

    for (int i = 0; i < 10;   i)
    {
        if (how_many_num[i] != -1)
        {
            cout << "Digit " << i << " was found " << how_many_num[i] << " times" << endl;
        }
    }
   
    cout << endl << "New string:" << str << endl;
}

Now, to translate that into standard library functions, try something like this:

#include <array>
#include <string>
#include <cctype>
...

void with_functions(string str)
{
    array<int, 10> how_many_num;
    how_many_num.fill(-1);

    for (char &ch : str)
    {
        if (isdigit(ch))
        {
              how_many_num[ch - '0'];
        }
        else if (isalpha(ch))
        {
            ch = ' ';
        }
    }

    for (int i = 0; i < 10;   i)
    {
        if (how_many_num[i] != -1)
        {
            cout << "Digit " << i << " is found " << how_many_num[i] << " times" << endl;
        }
    }
   
    cout << endl << "New string: " << str << endl;
}

Alternatively:

#include <array>
#include <string>
#include <map>
#include <cctype>
...

void with_functions(string str)
{
    map<char, int> how_many_num;

    for (char &ch : str)
    {
        if (isdigit(ch))
        {
              how_many_num[ch];
        }
        else if (isalpha(ch))
        {
            ch = ' ';
        }
    }

    for (const auto &elem : how_many_num)
    {
        cout << "Digit " << elem.first << " is found " << elem.second << " times" << endl;
    }
   
    cout << endl << "New string: " << str << endl;
}