HappyLeetcode37:Add Binary

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

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

这道题挺简单的，不多说了，代码奉上

class Solution {
public:
    string addBinary(string a, string b) {
        int lengtha = a.length();
        int lengthb = b.length();
        int indexa = a.length() - 1;
        int indexb = b.length() - 1;
        int res = 0;//设置进位
        string result;
        map<char, int> mapping;
        mapping['1'] = 1;
        mapping['0'] = 0;
        int value;
        while (indexa>=0||indexb>=0)
        {
            
            if (indexa < 0)
                value = 0 + mapping[b[indexb]] + res;
            else if (indexb < 0)
                value = mapping[a[indexa]] + 0 + res;
            else
                value = mapping[a[indexa]] + mapping[b[indexb]] + res;
            if (value >= 2)
            {
                res = 1;
                value %=2;
            }
            else
            {
                res = 0;
            }
            result.push_back(value+'0'-0);
            indexa--;
            indexb--;
        }
        if (res == 1)
            result.push_back(res + '0' - 0);
        reverse(result.begin(), result.end());
        return result;
    }
};