题解 | #数制转换#

用栈即可

#include<iostream>
#include<stack>
#include<string>
using namespace std;
int main(){
    string s;
    stack<char>ans;
    int a,b;
    while(cin>>a>>s>>b){
        long number=0;
        for(int i=0;i<s.size();i++){//a进制转十进制
            int x;
           if(s[i]>='a'&&s[i]<='f')x=s[i]-'a'+10;
            else if(s[i]>='A'&&s[i]<='F')x=s[i]-'A'+10;
            else x=s[i]-'0';
            number=number*a+x;
        }
        while(number!=0){//十进制转b进制
            int r=number%b;
            number=number/b;
            char c;
            if(r>9)c=r-10+'A';
            else c=r+'0';
            ans.push(c);
        }
        while(!ans.empty()){
            printf("%c",ans.top());
            ans.pop();
        }
        printf("\n");
    }
}