leetcode Add Binary

题目连接

https://leetcode.com/problems/add-binary/  

Add Binary

Description

Given two binary strings, return their sum (also a binary string).

For example, 
a = “11” 
b = “1” 
Return “100”.

class Solution {
public:
	string addBinary(string a, string b) {
		reverse(a.begin(), a.end());
		reverse(b.begin(), b.end());
		string ans = "";
		size_t n = a.length(), m = b.length();
		size_t i = 0, g = 0, c = min(n, m);
		for (; i < c; i++) {
			size_t k = a[i] - '0' + b[i] - '0' + g;
			ans += (k & 1) + '0';
			g = k >> 1;
		}
		string &t = a.length() > b.length() ? a : b;
		c = t.length();
		for (; i < c; i++) {
			size_t k = t[i] - '0' + g;
			ans += (k & 1) + '0';
			g = k >> 1;
		}
		if (g) ans += '1';
		reverse(ans.begin(), ans.end());
		return ans;
	}
};