Leetcode 67. 二进制求和

class Solution {
public:
    string addBinary(string a, string b) {
        if (a.size() < b.size()) return addBinary(b, a);
        reverse(a.begin(), a.end());
        reverse(b.begin(), b.end());
        int jin = 0, L = b.size(), i = 0;
        for (; i < L; ++i) {
            int t = jin + a[i] + b[i] - '0' - '0';
            a[i] = t % 2 + '0';
            jin = t / 2;
        }
        while (i < a.size() && jin == 1) {
            int t = jin + a[i] - '0';
            a[i] = t % 2 + '0';
            jin = t / 2;
            ++i;
        }
        if (jin == 1) a.push_back('1');
        reverse(a.begin(), a.end());
        return a;
    }
};