Add Binary

描述
Given two binary strings, return their sum (also a binary string).
For example,
a = “11”
b = “1”
Return 100.
分析
無

// Add Binary
// 時間複雜度O(n)，空間複雜度O(1)
class Solution {
    public String addBinary(String a, String b) {
        StringBuilder result = new StringBuilder();
        int i = a.length() - 1;
        int j = b.length() - 1;
        int carry = 0;
        
        while(i >= 0 || j >= 0 || carry > 0) {
            int valueA = i < 0 ? 0 : a.charAt(i--) - '0';
            int valueB = j < 0 ? 0 : b.charAt(j--) - '0';
            int sum = valueA + valueB + carry;
            result.insert(0, Character.forDigit(sum % 2, 10));
            carry = sum / 2;
        }
        return result.toString();
    }
}