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"

Problem Summary #

Given two binary strings, return their sum (represented in binary). The input consists of non-empty strings and contains only the digits 1 and 0.

Solution Approach #

• The requirement is to output the sum of 2 binary numbers, with the result also represented in binary.
• Easy problem. Just perform addition according to the rules of binary addition.

Code #

package leetcode

import (
	"strconv"
	"strings"
)

func addBinary(a string, b string) string {
	if len(b) > len(a) {
		a, b = b, a
	}

	res := make([]string, len(a)+1)
	i, j, k, c := len(a)-1, len(b)-1, len(a), 0
	for i >= 0 && j >= 0 {
		ai, _ := strconv.Atoi(string(a[i]))
		bj, _ := strconv.Atoi(string(b[j]))
		res[k] = strconv.Itoa((ai + bj + c) % 2)
		c = (ai + bj + c) / 2
		i--
		j--
		k--
	}

	for i >= 0 {
		ai, _ := strconv.Atoi(string(a[i]))
		res[k] = strconv.Itoa((ai + c) % 2)
		c = (ai + c) / 2
		i--
		k--
	}

	if c > 0 {
		res[k] = strconv.Itoa(c)
	}

	return strings.Join(res, "")
}