题解 | #数制转换#

#include<iostream>
#include<cstdio>
#include<string>
using namespace std;
int CharToInt(char x){
    if(x>='a'&&x<='f'){
        return x-'a'+10;
    }
    else if(x<='9'){
        return x-'0';
    }
    else{
        return x-'A'+10;
    }
}
char IntToChar(int x){
    if(x<=9){
        return x+'0';
    }
    else{
        return x-10+'A';
    }
}
int main(){
    int a,b;
    string n;
    while(cin>>a>>n>>b){
        if(n=="0"){
            printf("0");
        }
        else{
            long number=0;
            for(int i=0;i<n.size();++i){
                number*=a;
                number+=CharToInt(n[i]);
            }
            string resultant;
            while(number!=0){
                resultant+=IntToChar(number%b);
                number/=b;
            }
            for(int i=resultant.size()-1;i>=0;--i){
                printf("%c",resultant[i]);
            }
        }
        printf("\n");
    }
    return 0;
}