67. Add Binary

Problem:

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"

Analysis:
Skip

Solution:

class Solution {
    public String addBinary(String a, String b) {
        int i = a.length() - 1, j = b.length() - 1, carry = 0;
        StringBuilder sb = new StringBuilder();
        while(i >= 0 || j >= 0 ) {
            int x = i < 0 ? 0 : a.charAt(i) - '0';
            int y = j < 0 ? 0 : b.charAt(j) - '0';
            int cur = x + y + carry;
            sb.append(cur & 1);
            carry = cur >> 1;
            i--;
            j--;
        }
        if (carry == 1)
            sb.append(carry);
        return sb.reverse().toString();
    }
}