67. Add Binary

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

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

class Solution {public:    string addBinary(string a, string b) {      string result="";    int a_length=a.length()-1;    int b_length=b.length()-1;    int sum=0;    int count=0;    while(a_length>=0||b_length>=0)    {        int a_temp=0<=a_length?(a[a_length]-'0'):0;        int b_temp=0<=b_length?(b[b_length]-'0'):0;        sum=a_temp+b_temp+count;        result=to_string(sum%2)+result;        count=sum/2;        a_length=a_length>=0?(a_length-1):-1;        b_length=b_length>=0?(b_length-1):-1;    }    if(count!=0) result=to_string(count)+result;    return result;    }};