LeetCode 67. Add Binary

原题链接在这里: https://leetcode.com/problems/add-binary/

题目：

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

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

题解：

Have sum = current pointing value of a + current pointing value of b + carry.

If current point value is out of index bound, then use 0.

Time Complexity: O(max(a.length(), b.length())).

Space O(max(a.length(), b.length())).

AC Java: 

class Solution {
    public String addBinary(String a, String b) {
        int len1 = a.length();
        int len2 = b.length();
        int i = len1-1;
        int j = len2-1;
        int carry = 0;
        StringBuilder sb = new StringBuilder();
        while(i>=0 || j>=0 || carry >0){
            carry += i>=0 ? a.charAt(i)-'0' : 0;
            carry += j>=0 ? b.charAt(j)-'0' : 0;
            sb.insert(0, carry%2);
            carry /= 2;
            
            i--;
            j--;
        }
        
        return sb.toString();
    }
}

类似Plus One, Add Strings.