Add Binary

Traverse backwards

class Solution {public:    string addBinary(string a, string b) {        string res="";        int c=0;        int i=a.size()-1, j=b.size()-1;        while (i>=0||j>=0||c) {            int cur=c;            if (i>=0) cur+=a[i]-'0';            if (j>=0) cur+=b[j]-'0';            c=cur/2;            cur=cur%2;            res.insert(0, 1, cur+'0');            i--;            j--;        }        return res;    }};