1674 - Minimum Moves to Make Array Complementary.

Medium

You are given an integer array nums of even length n and an integer limit. In one move, you can replace any integer from nums with another integer between 1 and limit, inclusive.

The array nums is complementary if for all indices i ( 0-indexed ), nums[i] + nums[n - 1 - i] equals the same number. For example, the array [1,2,3,4] is complementary because for all indices i, nums[i] + nums[n - 1 - i] = 5.

Return the minimum number of moves required to make nums complementary.

Example 1:

Input: nums = 1,2,4,3, limit = 4

Output: 1

Explanation: In 1 move, you can change nums to 1,2,2,3 (underlined elements are changed).

nums0 + nums3 = 1 + 3 = 4.

nums1 + nums2 = 2 + 2 = 4.

nums2 + nums1 = 2 + 2 = 4.

nums3 + nums0 = 3 + 1 = 4.

Therefore, numsi + numsn-1-i = 4 for every i, so nums is complementary.

Example 2:

Input: nums = 1,2,2,1, limit = 2

Output: 2

Explanation: In 2 moves, you can change nums to 2,2,2,2. You cannot change any number to 3 since 3 > limit.

Example 3:

Input: nums = 1,2,1,2, limit = 2

Output: 0

Explanation: nums is already complementary.

Constraints:

• n == nums.length

• <code>2 <= n <= 10⁵</code>

• <code>1 <= numsi<= limit <= 10⁵</code>

• n is even.