Java for LeetCode 067 Add Binary

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

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

解题思路：

JAVA实现如下：

static public String addBinary(String a, String b) {if (a.length() < b.length()) {String temp = a;a = b;b = temp;}boolean carry = false;StringBuilder sb = new StringBuilder(a);for (int i = 0; i < b.length(); i++) {if (b.charAt(b.length() - 1 - i) == '0') {if (sb.charAt(a.length() - 1 - i) == '0' && carry) {sb.replace(a.length() - 1 - i, a.length() - i, "1");carry = false;} else if (sb.charAt(a.length() - 1 - i) == '1' && carry)sb.replace(a.length() - 1 - i, a.length() - i, "0");} else {if (sb.charAt(a.length() - 1 - i) == '0' && !carry)sb.replace(a.length() - 1 - i, a.length() - i, "1");else if (sb.charAt(a.length() - 1 - i) == '1' && !carry) {sb.replace(a.length() - 1 - i, a.length() - i, "0");carry = true;}}}if (!carry)return sb.toString();for (int i = a.length() - b.length() - 1; i >= 0; i--)if (sb.charAt(i) == '0') {sb.replace(i, i + 1, "1");return sb.toString();} elsesb.replace(i, i + 1, "0");sb.insert(0, '1');return sb.toString();}