Watch 10 video solutions for Maximum Alternating Subsequence Sum, a medium level problem involving Array, Dynamic Programming. This walkthrough by CrioDo has 304,649 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.
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.
[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 [4,2,3,7,2,1,4] (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 = [5,6,7,8] 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:
1 <= nums.length <= 1051 <= nums[i] <= 105