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1144. Decrease Elements To Make Array Zigzag

Difficulty Topics

Description

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

Solution

decrease-elements-to-make-array-zigzag.py
class Solution:
    def movesToMakeZigzag(self, A: List[int]) -> int:
        n = len(A)

        def helper(start):
            nums = A[:]
            count = 0

            for i in range(start, n, 2):
                if i - 1 >= 0 and nums[i] <= nums[i - 1]:
                    move = max(0, nums[i] - 1)

                    if nums[i] > move:
                        count += abs(move - nums[i - 1])
                        nums[i - 1] = move
                    else:
                        return float('inf')

                if i + 1 < n and nums[i] <= nums[i + 1]:
                    move = max(0, nums[i] - 1)

                    if nums[i] > move:
                        count += abs(move - nums[i + 1])
                        nums[i + 1] = move
                    else:
                        return float('inf')


            return count

        return min(helper(0), helper(1))