Add Binary

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

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

 

public class Solution {
    public String addBinary(String a, String b) {
        int lenA = a.length();
        int lenB = b.length();
        int carry = 0;
        String res = "";
        int len = Math.max(lenA, lenB);
        for (int i = 0; i < len; i++) {
        	int m;
        	int n;
        	if (i < lenA) {
        		m = a.charAt(lenA-i-1) - '0';
        	} else {
        		m = 0;
        	}
        	if (i < lenB) {
        		n = b.charAt(lenB-i-1) - '0';
        	} else {
        		n = 0;
        	}
        	int temp = m+n+carry;
        	carry = temp/2;
        	res = temp % 2 + res;;
        }
        return (carry==0) ? res : carry+res;
    }
}