Leetcode Add Binary

二进制求和。注意进位就可以了。

class Solution {public:    string addBinary(string a, string b) {        string ans;        int carry = 0, num;        for(int i = 0; i < max(a.size(), b.size()); i++){            char c1 = i < a.size() ? a[a.size()-i-1] : '0';            char c2 = i < b.size() ? b[b.size()-i-1] : '0';            num = (c1-'0') + (c2-'0') + carry;            carry = num /2;            ans = char(num%2 + '0') + ans;        }        if(carry){            ans = '1' + ans;        }        return ans;    }};