67. Add Binary【LeetCode】

67. 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) {
        String res ="";
        int l1=a.length()-1;
        int l2=b.length()-1;
        
        int carry=0;
        for(int i=l1,j=l2;i>=0||j>=0;i--,j--){
            int sum=carry;
            sum+=(i>=0)?(int)(a.charAt(i)-'0'):0;
            sum+=(j>=0)?(int)(b.charAt(j)-'0'):0;
            res =sum%2+res;
            carry=sum/2;
            
        }
        if(carry!=0){
            res=carry+res;
        }
        return res;
    }
}