[Swift]LeetCode1073. 负二进制数相加 | Adding Two Negabinary Numbers

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Given two numbers arr1 and arr2 in base -2, return the result of adding them together.

Each number is given in array format:  as an array of 0s and 1s, from most significant bit to least significant bit.  For example, arr = [1,1,0,1] represents the number (-2)^3 + (-2)^2 + (-2)^0 = -3.  A number arr in array format is also guaranteed to have no leading zeros: either arr == [0] or arr[0] == 1.

Return the result of adding arr1 and arr2 in the same format: as an array of 0s and 1s with no leading zeros.

Example 1:

Input: arr1 = [1,1,1,1,1], arr2 = [1,0,1]
Output: [1,0,0,0,0]
Explanation: arr1 represents 11, arr2 represents 5, the output represents 16. 

Note:

1. 1 <= arr1.length <= 1000
2. 1 <= arr2.length <= 1000
3. arr1 and arr2 have no leading zeros
4. arr1[i] is 0 or 1
5. arr2[i] is 0 or 1

---

给出基数为 -2 的两个数 arr1 和 arr2，返回两数相加的结果。

数字以 数组形式 给出：数组由若干 0 和 1 组成，按最高有效位到最低有效位的顺序排列。例如，arr = [1,1,0,1] 表示数字 (-2)^3 + (-2)^2 + (-2)^0 = -3。数组形式 的数字也同样不含前导零：以 arr 为例，这意味着要么 arr == [0]，要么 arr[0] == 1。

返回相同表示形式的 arr1 和 arr2 相加的结果。两数的表示形式为：不含前导零、由若干 0 和 1 组成的数组。 

示例：

输入：arr1 = [1,1,1,1,1], arr2 = [1,0,1]
输出：[1,0,0,0,0]
解释：arr1 表示 11，arr2 表示 5，输出表示 16 。 

提示：

1. 1 <= arr1.length <= 1000
2. 1 <= arr2.length <= 1000
3. arr1 和 arr2 都不含前导零
4. arr1[i] 为 0 或 1
5. arr2[i] 为 0 或 1

---

Runtime: 36 ms

Memory Usage: 21.4 MB

class Solution {
    func addNegabinary(_ arr1: [Int], _ arr2: [Int]) -> [Int] {
        var arr1 = [Int](arr1.reversed())
        var arr2 = [Int](arr2.reversed())
        var result:[Int] = [Int]()
        var carry:Int = 0
        var i:Int = 0
        while(i < arr1.count || i < arr2.count || carry != 0)
        {
            let num1:Int = i < arr1.count ? arr1[i] : 0
            let num2:Int = i < arr2.count ? arr2[i] : 0
            let x:Int =  num1 + num2 + carry
            result.append((x + 2) % 2)
            carry = (x - result.last!) / -2
            i += 1
        }
        while(result.count > 1 && result.last! == 0)
        {
            result.removeLast()
        }
        return result.reversed()
    }
}