67. Add Binary

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"难度: easy题目：给定两个二进制字符串，返回它们的和（也是二进制字符串）。字符串都不为空且只有0､1组成。Runtime: 2 ms, faster than 95.70% of Java online submissions for Add Binary.Memory Usage: 26.2 MB, less than 54.54% of Java online submissions for Add Binary.public class Solution { public String addBinary(String a, String b) { int i = a.length() - 1, j = b.length() - 1, carry = 0; StringBuilder result = new StringBuilder(); while (i >= 0 || j >= 0) { char ac = i >= 0 ? a.charAt(i) : ‘0’; char bc = j >= 0 ? b.charAt(j) : ‘0’; int sum = (ac - ‘0’) + (bc - ‘0’) + carry; result.append(sum % 2); carry = sum / 2; i–; j–; } if (carry > 0) { result.append(1); } return new String(result.reverse()); }}