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. - 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 arra