1144. Decrease Elements To Make Array Zigzag
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
Solutions
Solution 1: Enumeration + Greedy
We can separately enumerate the even and odd positions as the elements "smaller than adjacent elements", and then calculate the required number of operations. The minimum of the two is taken.
The time complexity is $O(n)$, where $n$ is the length of the array $nums$. The space complexity is $O(1)$.
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