Add Binary

/*两个二进制相加，求和*/
class Solution {
public:
    string addBinary(string a, string b) {
        string ans="";
        int i = a.length() -1,j = b.length() -1;
        int c = 0;
        while(i>=0 || j>=0 ||c == 1){
            if(i>=0) {c+= a[i]-'0';i--;}
            if(j>=0) {c+= b[j]-'0';j--;}
            ans = char(c%2+'0')+ans;//这里就完成了反转
            c/=2;
        }
        return ans;
    }
};