[LeetCode]Add Binary

题目描述：

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

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

解题方案：

class Solution {
public:
    string addBinary(string a, string b) {
        int LocationA = a.size() - 1;
        int LocationB = b.size() - 1;

        if (LocationA == -1) {
            return b;
        }
        if (LocationB == -1) {
            return a;
        }
        string result;
        int carry = 0;

        while((LocationA >= 0) && (LocationB >= 0)) {
            int temp = ((a[LocationA] - '0') + (b[LocationB] - '0') + carry) % 2;
            carry    = ((a[LocationA] - '0') + (b[LocationB] - '0') + carry) / 2;
            result.append(1, temp + '0');
            --LocationA;
            --LocationB;
        }
        if (LocationA != -1) {
            while(LocationA >= 0) {
                int temp = ((a[LocationA] - '0') + carry) % 2;
                carry    = ((a[LocationA] - '0') + carry) / 2;
                result.append(1, temp + '0');
                --LocationA;
            }
        }
        if (LocationB != -1) {
            while(LocationB >= 0) {
                int temp = ((b[LocationB] - '0') + carry) % 2;
                carry    = ((b[LocationB] - '0') + carry) / 2;
                result.append(1, temp + '0');
                --LocationB;
            }
        }

        if (carry != 0) {
            result.append(1, carry + '0');
        }

        int i = 0;
        int j = result.size() - 1;
        //将字符串反转
        while (i <= j) {
            char temp = result[i];
            result[i] = result[j];
            result[j] = temp;
            ++i;
            --j;
        }
        return result;
    }
};