Leetcode67： 二进制求和

题目

给定两个二进制字符串，返回他们的和（用二进制表示）。

输入为非空字符串且只包含数字 1 和 0。

示例 1:

输入: a = "11", b = "1"
输出: "100"

示例 2:

输入: a = "1010", b = "1011"
输出: "10101"

Swift解法

class Solution {
        func addBinary(_ a: String, _ b: String) -> String {
            let zero = Character("0")
            let one = Character("1")
            let a = a.map({$0})
            let b = b.map({$0})
            let count = max(a.count, b.count)
            var character = [Character](repeating: zero, count: count)
            var i = 0
            var flag: UInt8 = 0
            while i <= count - 1 {
                let aindex = a.count - i - 1
                let bindex = b.count - i - 1
                let index = count - i - 1
                var sum = flag
                if aindex >= 0 && a[aindex] == one { sum += 1 }
                if bindex >= 0 && b[bindex] == one { sum += 1 }
                character[index] = (sum % 2 > 0) ? one : zero
                flag = (sum >= 2) ? 1 : 0
                i += 1
            }
            if flag == 1 {
                character.insert(one, at: 0)
            }
            return String(character)
        }
}

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/add-binary