Given two binary strings, return their sum (also a binary string).
The input strings are both non-empty and contains only characters 1 or 0.
Example 1:
Input: a = "11", b = "1"
Output: "100" Example 2:Input: a = "1010", b = "1011"
Output: "10101"class Solution { public String addBinary(String a, String b) { StringBuilder sb = new StringBuilder(); int i = a.length()-1, j = b.length()-1, carry = 0; while(i >= 0 || j >= 0){ int sum = carry; if(i >= 0) sum += a.charAt(i--) - '0'; if(j >= 0) sum += b.charAt(j--) - '0'; sb.append(sum % 2); carry = sum / 2; } if(carry != 0) sb.append(carry); return sb.reverse().toString(); }}