Перевод строки в число

#include <iostream>
#include <string>
#include <stdlib.h>
#include <iomanip>
 
using namespace std;
 
double change (string);
 
int main ()
{
setlocale (LC_ALL, "Russian");
string s;
char answ;
double number;
do
{
cout << "Введите строку:\n";
getline (cin, s);
number = change(s);
cout << "\nВы ввели число: " << setiosflags(ios::fixed)
<< setiosflags (ios::showpoint) << setprecision (2)
<< setw (15) << number;
cout << "\nПродолжить (y/n)??? "; cin >> answ;
}
while (answ != 'n');
cout << endl;
return 0;
}
 
double change (string ss)
{
const int MAX = 20;
char masone[MAX], mastwo[MAX];
int l = ss.length ();
int count = 0;
ss.copy (masone, l, 0);
masone[l] = '\0';
char check;
for (int j = 0; j < l; j++)
{
check = masone[j];
switch (check)
{
case '0': mastwo[count++] = masone[j]; break;
case '1': mastwo[count++] = masone[j]; break;
case '2': mastwo[count++] = masone[j]; break;
case '3': mastwo[count++] = masone[j]; break;
case '4': mastwo[count++] = masone[j]; break;
case '5': mastwo[count++] = masone[j]; break;
case '6': mastwo[count++] = masone[j]; break;
case '7': mastwo[count++] = masone[j]; break;
case '8': mastwo[count++] = masone[j]; break;
case '9': mastwo[count++] = masone[j]; break;
case '.': mastwo[count++] = masone[j]; break;
}
}
mastwo[count] = '\0';
double result = strtod (mastwo, '\0');
return result;
}

////// решение примеров
 
#include <iostream>
#include <iomanip>
#include <string>
 
using namespace std;
 
const int MAX = 30;
 
class bigproblem
{
private:
    char str[MAX];
public:
    bigproblem ()
    { str[0] = 0; }
    void showstr ()
    { cout << str << endl; }
    long double mstold (string);
};
 
long double bigproblem::mstold (string ss)
{
    int l = ss.size();
    int count = 0;
    for (int j = 0; j < l; j++)
    {
        switch (ss[j])
        {
        case '0': str[count++] = ss[j]; break;
        case '1': str[count++] = ss[j]; break;
        case '2': str[count++] = ss[j]; break;
        case '3': str[count++] = ss[j]; break;
        case '4': str[count++] = ss[j]; break;
        case '5': str[count++] = ss[j]; break;
        case '6': str[count++] = ss[j]; break;
        case '7': str[count++] = ss[j]; break;
        case '8': str[count++] = ss[j]; break;
        case '9': str[count++] = ss[j]; break;
        case '.': str[count++] = ss[j]; break;
        }
    }
    str[count] = 0;
    long double result = stold (str);
    return result;
}
 
int main ()
{
    string s;
    bigproblem bp;
    char answ;
    long double end;
    do
    {
        cout << "Enter money string:\n";
        getline (cin, s);
        end = bp.mstold (s);
        cout << "You entered: ";
        cout << setiosflags (ios::fixed) << setiosflags (ios::showpoint)
            << setprecision (2) << setw (15) << end << endl;
        cout << "One more time (y/n)??? "; cin >> answ;
    }
    while (answ != 'n');
    cout << endl;
    return 0;
}