大数数制转换

#include<iostream>
#include<string>
using namespace std;
int a[100];
string Convert(string s,int m,int n){        
    for (int i=0;i<s.length();i++){
        if (s[i]>='0' && s[i]<='9'){
            a[i] = s[i] - '0';
        }else{
            a[i] = s[i] - 'a' + 10;
        }
        //sum = sum*m + a[i];        //数太大会爆掉，要留到下个循环，边累加边取余 
    }
    string ans;
    while (true){
        for(int i=0;i<s.length();i++){
            cout<<a[i]<<" ";
        } 
        cout<<endl;
        int flag = 0;
        for(int i=0;i<s.length();i++){
            if(a[i]!=0){
                  flag = 1;
                   break;
               }
        }
        if(flag == 0){
            break;
        }
        long long sum = 0;
        for(int i=0;i<s.length();i++){    //每过一次while循环 
            sum = sum*m+a[i];
            sum = sum%n;
        }
        if(sum>=0 && sum<=9){
            char ch = sum + '0';
            ans += ch;
        }else{
            char ch = sum-10+'a';
            ans += ch;
        }
        int point=0;
        for(int i=0;i<s.length();i++)    //作用：将数除以n；  比如123456789 -> 003429355 
        {
            a[i] += point*m;    
            point = a[i]%n;
            a[i] /= n;    
        }
    }
    for(int i=0,j=ans.length()-1;i<j;i++,j--){
        char ch = ans[i];
        ans[i] = ans[j];
        ans[j] = ch;
    }
    return ans;
}
int main()
{
    int m,n;
    string s;
    while(cin>>m){
        cin>>n;
        cin>>s;
        for(int i=0;i<s.length();i++){
            if(s[i]>='A' && s[i]<='Z'){
                s[i] = s[i]+32;
            }
        }
        cout<<Convert(s,m,n)<<endl;
    }
    return 0;
}