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;
     }
 }