67. Add Binary

Description

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.

Constraints

• Each string consists only of '0' or '1' characters.

• 1 <= a.length, b.length <= 10^4

• Each string is either "0" or doesn't contain any leading zero.

Approach

Links

• GeeksforGeeks

• Leetcode

• ProgramCreek

Examples

Example 1

Input: a = "11", b = "1"

Output: "100"

Example 2

Input: a = "1010", b = "1011"

Output: "10101"

Solutions

Solution 1

/**
 * 
 * 
 */

class Solution {
    public String addBinary(String a, String b) {
        int alen = a.length();
        int blen = b.length();
        int sum = 0;
        StringBuilder result = new StringBuilder("");
        while(alen > 0 || blen > 0) {
            if(alen > 0 && a.charAt(--alen) == '1') {
                sum++;
            }
            if(blen > 0 && b.charAt(--blen) == '1') {
                sum++;
            }
            result.insert(0, (sum%2));
            sum /= 2;
        }
        if(sum == 1) {
            result.insert(0, "1");
        }
        return result.toString();
    }
}

Solution 2

/**
 * 
 * 
 */

class Solution {
    public String addBinary(String a, String b) {
        int alen = a.length();
        int blen = b.length();
        int sum = 0;
        StringBuilder result = new StringBuilder("");
        while(alen > 0 || blen > 0) {
            sum += (alen > 0)? a.charAt(--alen)-'0': 0;
            sum += (blen > 0)? b.charAt(--blen)-'0': 0;
            result.append(sum&1);
            sum /= 2;
        }
        if(sum == 1) {
            result.append(1);
        }
        return result.reverse().toString();
    }
}

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