進制轉換

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


char radix(unsigned long long int i)
{
    if (i >= 10)
    {
        return i + 55;
    }
    else if (i >= 0 && i <= 9)
    {
        return i + 48;
    }
}

bool chk(unsigned long long int b, unsigned long long int a)
{
    while (a != 0)
    {
        if (a % 10 >= b)
        {
            return 1;
        }
        a /= 10;
    }
    return 0;
}
unsigned long long int true_value(unsigned long long int b, unsigned long long int a)
{
    unsigned long long  int c;
    unsigned long long  int i = 0;
    unsigned long long  int sum = 0;
    while (a > 0)
    {
        sum += (a%10)*pow(b, i);
        a /= 10;
        i++;
    }

    return sum;
}

void convert(unsigned long long int a, unsigned long long int b)
{
    char c[100] = {};

    unsigned long long  int i = 0,d;
    while (a > 0)
    {
        d = a%b;
        c[i] = radix(d);
        a /= b;
        i++;
    }
    for (int i = 99; i >= 0; i--)
    {
        if(c[i] != 0)
        cout << c[i];
    }
}

int main()

{
    unsigned long long  int or_base, or_radix;
    unsigned long long  int af_base;
    cout << "輸入待轉換進制" << endl;;
    cin >> or_base;
    cout << "輸入待轉換值" << endl;
    cin >> or_radix;
    if (chk(or_base, or_radix)==1)
    {
        cout << "輸入錯誤" << endl;
        system("PAUSE");
        return 0;
    }
    cout <<"輸入同等於的10進位值"<< true_value(or_base, or_radix) << endl;
    cout << "輸入轉換後的進制值" << endl;
    cin >> af_base;
    cout << "轉換後的數字為"<<endl;
    convert(true_value(or_base, or_radix), af_base);

    system("PAUSE");
    return 0;
}