c ++，从x数系统到小数的转换器

Question

I wrote this code it seemed to good but the output is always 0 what could be the problem? I m just writing a code to convert from x number system to decimal.

    #include <string>
    #include <iostream>
    using namespace std;

int main() {

string str;
long szam = 0, Dec, num, Base = 1, x,i=1;
cout << "the number : ";
cin >> str;
cout << "The input number system:";
cin >> x;

   while (str[i] == '\0')
     {
       if (str[i] = 'A') { num = 10;}
       else if (str[i] = 'B') { num = 11; }
       else if (str[i] = 'C') { num = 12; }
       else if (str[i] = 'D') { num = 13; }
       else if (str[i] = 'E') { num = 14; }
       else if (str[i] = 'F') { num = 15; }
       else { num = str[i] - '0'; }

       Dec = Dec + num * Base;
       Base = Base * x;

      }
cout << szam << endl;
return 0;

}

If x smaller than 10 its easy but i cant handle the 10+ system because of the letter use of numbers.

Answer 1

1. Your i should start from 0, not from 1.

2. Your i should be incremented within your loop. As it stands right now, i is never incremented, so it always has the value of 1 , so you are only ever looking at str[1] .

3. Your loop should continue while str[i] != '\\0' , not while str[i] == '\\0' .

4. You might want to consider handling the case of not only the letters ABCDEF but also the letters abcdef .

Answer 2

您应该使用std :: stol完全满足您的需求。