C++ 这题简单

#include<string>
#include<algorithm>
using namespace std;
//对s除以2
string div2(string s) {
	//cout << "div2输入：s=" << s << endl;
	while (s[0] == '0') {//去掉左侧的零
		s.erase(0, 1);
	}
	if (s == "")return "0";

	//一般情况
	int carry = 0;
	for (int i = 0; i < s.size(); i++) {
		if ((s[i] +carry - '0') % 2 == 1) {
			s[i] = (s[i] + carry - '0') / 2 + '0';
			carry = 10;
		}
		else {
			s[i] = (s[i] + carry - '0') / 2 + '0';
			carry = 0;
		}
	}
	while (s[0] == '0') {//去掉左侧的零
		s.erase(0, 1);
	}
	//cout << "div2结果：s=" << s << endl;
	return s;
}
//将s转成二进制数,采用除2取余法
string f(string s) {
	if (s == "" || s == "0")return "0";

	string res = "";
	while (s != "") {
		res += (s[s.size() - 1] - '0') % 2 + '0';
		s = div2(s);
	}

	reverse(res.begin(), res.end());
	return res;
}
int main() {
	string s;
	while (cin >> s) {
		cout << f(s) << endl;
	}
	return 0;
}