题解 | #数制转换#

#include <bits/stdc++.h>

using namespace std;

int main(){
	
	string a_line, b_line;
	int a;
	int b;
	while (cin >> a >> a_line >> b){
		vector<int> num;
		
		for (int i=0; i<a_line.size(); i++){
			if (isdigit(a_line[i])){
				num.push_back(a_line[i] - '0'); 
			}
			else if (a_line[i] >= 'A' && a_line[i] <= 'Z'){
				num.push_back(a_line[i] - 'A' + 10);
			}
			else if (a_line[i] >= 'a' && a_line[i] <= 'z'){
				num.push_back(a_line[i] - 'a' + 10); 
			}
		}
		
		reverse(num.begin(), num.end());
		
		vector<int> res;
		while (num.size()){
			int r = 0;
			
			for (int i=num.size()-1; i>=0; i--){
				num[i] = num[i] + a*r;
				r = num[i] % b;
				num[i] = num[i] / b;
			}
			res.push_back(r);
			
			while (num.size() && num.back() == 0) num.pop_back();
			
		}
		reverse(res.begin(), res.end());
		
		for (auto item : res){
			if (item >=0 && item <= 9) cout << item;
			else {
				cout << char(item-10+'A');
			}
		} 
		puts("");
		
	}
	
	
	
	return 0;
}