Remove pairs of elements from the ends of an array, keeping the pair sum fixed, and maximize the number of valid operations.
You are given an integer array nums. In one operation, you may remove exactly two elements from the array, and the removed pair must come from the current ends of the array. More precisely, in each move you may remove:
All chosen pairs must have the same sum. Your task is to determine the maximum number of operations you can perform.
The key idea is to choose a target sum based on the first operation, then simulate or count how many valid removals can be made while the array shrinks.
nums: an integer array of length at least 2.The exact platform input is an array of integers.
Return a single integer: the maximum number of valid operations with the same pair sum.
2 <= nums.lengthExact platform constraints are not provided here; use the standard LeetCode-style interpretation.
Example 1
Input
nums = [3,2,1,2,3,4]
Output
3
Explanation
One optimal sequence is to remove [3,4]? No, that is not from the ends. Instead, choose a valid target sum using end pairs and keep removing valid end pairs until impossible. The maximum number of operations is 3.
Example 2
Input
nums = [1,1,1,1]
Output
2
Explanation
Remove the first two elements twice, each time with sum 2.
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