LEETCODE: Add Binary

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

For example,
a = "11"
b = "1"
Return "100".

二进制！

class Solution {public:    string addBinary(string a, string b) {        int longstr = a.length() > b.length() ? a.length() : b.length();        int shortstr = a.length() < b.length() ? a.length() : b.length();        string result(longstr + 1, '0');        int jinwei = 0;        int ii = 0;                //Calculate if both string has value.        for(; ii < shortstr; ii ++) {            int sum = a[a.length() - 1 - ii] - '0' + b[b.length() - 1 - ii] -'0' + jinwei;            if(sum >= 2) {                jinwei = 1;                sum = sum % 2;            }            else {                jinwei = 0;            }            result[result.length() - 1 - ii] = sum + '0';        }                //Calculate the remain string.        string &remain = a.length() > b.length() ? a : b;        for(; ii < longstr; ii ++) {            int sum = remain[remain.length() - 1 - ii] - '0' + jinwei;            if(sum >= 2) {                jinwei = 1;                sum = sum % 2;            }            else {                jinwei = 0;            }            result[result.length() - 1 - ii] = sum + '0';        }                //Set if there is jinwei.        if(jinwei == 1) {            result[0] = '1';        }        else {            result = result.substr(1, result.length() - 1);        }                return result;    }};