{leetcode}/problems/maximum-alternating-subsequence-sum/[LeetCode - 1911. Maximum Alternating Subsequence Sum ^]
The alternating sum of a 0-indexed array is defined as the sum of the elements at even indices minus the sum of the elements at odd indices.
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For example, the alternating sum of
[4,2,5,3]is(4 + 5) - (2 + 3) = 4.
Given an array nums, return the maximum alternating sum of any subsequence of _`nums` (after reindexing the elements of the subsequence)_.
A subsequence of an array is a new array generated from the original array by deleting some elements (possibly none) without changing the remaining elements' relative order. For example, [2,7,4] is a subsequence of 2,3,7,2,1,4] (the underlined elements), while [2,4,2] is not.
Example 1:
Input: nums = 4,2,5,3] Output: 7 Explanation: It is optimal to choose the subsequence [4,2,5] with alternating sum (4 + 5) - 2 = 7.
Example 2:
Input: nums = 8]
Output: 8
Explanation: It is optimal to choose the subsequence [8] with alternating sum 8.
Example 3:
Input: nums = 6,2,1,2,4,5] Output: 10 Explanation: It is optimal to choose the subsequence [6,1,5] with alternating sum (6 + 5) - 1 = 10.
Constraints:
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1 ⇐ nums.length ⇐ 105 -
1 ⇐ nums[i] ⇐ 105