[Swift]LeetCode1144.递减元素使数组呈锯齿状|DecreaseElementsToMakeArrayZigzag ...

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Given an array nums of integers, a move consists of choosing any element and decreasing it by 1.

An array A is a zigzag array if either:

Every even-indexed element is greater than adjacent elements, ie. A[0] > A[1] < A[2] > A[3] < A[4] > ...
OR, every odd-indexed element is greater than adjacent elements, ie. A[0] < A[1] > A[2] < A[3] > A[4] < ...

Return the minimum number of moves to transform the given array nums into a zigzag array.

Example 1:

Input: nums = [1,2,3]
Output: 2
Explanation: We can decrease 2 to 0 or 3 to 1.

Example 2:

Input: nums = [9,6,1,6,2]
Output: 4

Constraints:

1 <= nums.length <= 1000
1 <= nums[i] <= 1000

给你一个整数数组 nums，每次操作会从中选择一个元素并将该元素的值减少 1。

如果符合下列情况之一，则数组 A 就是锯齿数组：

每个偶数索引对应的元素都大于相邻的元素，即 A[0] > A[1] < A[2] > A[3] < A[4] > ...
或者，每个奇数索引对应的元素都大于相邻的元素，即 A[0] < A[1] > A[2] < A[3] > A[4] < ...

返回将数组 nums 转换为锯齿数组所需的最小操作次数。

示例 1：

输入：nums = [1,2,3]
输出：2
解释：我们可以把 2 递减到 0，或把 3 递减到 1。

示例 2：

输入：nums = [9,6,1,6,2]
输出：4

提示：

1 <= nums.length <= 1000
1 <= nums[i] <= 1000

4ms

 1 class Solution {
 2     func movesToMakeZigzag(_ nums: [Int]) -> Int {
 3         if nums.count < 3 {
 4             return 0
 5         }
 6         
 7         let n = nums.count
 8         var result1 = 0
 9         var result2 = 0
10         
11         var i = 1
12         while i < n {
13             var minValue = min(nums[i-1], i+1 < n ? nums[i+1] : 1000)
14             if minValue <= nums[i] {
15                 result1 += (nums[i]-minValue+1)
16             }
17             i += 2
18         }
19         
20         i = 0
21         while i < n {
22             var minValue = min(i > 0 ? nums[i-1] : 1000, i+1 < n ? nums[i+1] : 1000)
23             if minValue <= nums[i] {
24                 result2 += (nums[i]-minValue+1)
25             }
26             i += 2
27         }
28         
29         return min(result1, result2)
30     }
31 }

8ms

 1 class Solution {
 2     func movesToMakeZigzag(_ nums: [Int]) -> Int {
 3         var result = [0, 0]
 4         let n = nums.count 
 5         var left = 0
 6         var right = nums.count - 1
 7         
 8         for i in 0..<n {
 9             left = i > 0 ? nums[i-1] : 1001
10             right = i + 1 < n ? nums[i+1] : 1001
11             result[i%2] += max(0, nums[i] - min(left, right) + 1)
12         }
13         return result.min()!
14     }
15 }

Runtime: 8 ms

Memory Usage: 20.8 MB

 1 class Solution {
 2     func movesToMakeZigzag(_ nums: [Int]) -> Int {
 3         var n:Int = nums.count
 4         var j:Int = 0
 5         var s:Int = 0
 6         var t:Int = 0
 7         for i in stride(from:0,to:n,by:2)
 8         {
 9             j = 0
10             if i != 0
11             {
12                 j = max(j,nums[i]-nums[i-1]+1)
13             }
14             if i + 1 < n
15             {
16                 j = max(j,nums[i]-nums[i+1]+1)
17             }
18             s += j
19         }
20         for i in stride(from:1,to:n,by:2)
21         {
22             j = 0
23             if i != 0
24             {
25                 j = max(j,nums[i]-nums[i-1]+1)
26             }
27             if i + 1 < n
28             {
29                 j = max(j,nums[i]-nums[i+1]+1)
30             }
31             t += j
32         }
33         return min(s,t)       
34     }
35 }

12ms

 1 class Solution {
 2     func movesToMakeZigzag(_ nums: [Int]) -> Int {
 3         var movesA = 0
 4         var movesB = 0
 5         var array = nums
 6         for i in stride(from: 1, to: array.count, by: 2) {
 7             while array[i - 1] <= array[i] {
 8                     movesA += 1
 9                     array[i] -= 1
10                 }
11             
12             guard (i + 1) < array.count else { break }
13             
14             while array[i + 1] <= array[i] {
15                     movesA += 1
16                     array[i] -= 1
17                 }
18         }
19         array = nums
20         for i in stride(from: 1, to: array.count, by: 2) {
21             while array[i - 1] >= array[i] {
22                     movesB += 1
23                     array[i - 1] -= 1
24                 }
25             
26             guard (i + 1) < array.count else { break }
27             
28             while array[i + 1] >= array[i] {
29                     movesB += 1
30                     array[i + 1] -= 1
31                 }
32         }
33         
34         return movesA < movesB ? movesA : movesB
35     }
36 }