进制转换问题

#include <cstdio>
using namespace std;
string (int x, int n){
	const string a = "0123456789ABCDEF";
	string s = "";
	if(x == 0)
		return "0";
	while(x > 0){
		s = a[x%n] + s;
		x /= n;
	}
	return s;
}
int main(){
	int x, n;
	cin >> x >> n;
	cout << fun(x, n) << endl;
	
	system("pause");
	return 0;
}

#include <string>
using namespace std;
int (int n, string s){
	int i, t=0;
	for(i=0;i<=s.size();i++){
		if(s[i]>='0' && s[i]<'9'){
			t = t*n+s[i]-48;
		}
		if(s[i]>='A' && s[i]<='F'){
			t = t*n+s[i]-55;
		}
		if(s[i]>='a' && s[i]<='f'){
			t = t*n+s[i]-87;
		}
	}
	return t;
}
int main(){
	int n;
	string str;
	cin >> n >> str;
	cout << fun(n, str) << endl;
	
	system("pause");
	
	return 0;
}