{leetcode}/problems/find-the-maximum-length-of-valid-subsequence-i/[LeetCode - 3201. Find the Maximum Length of Valid Subsequence I ^]
You are given an integer array nums.
A <span data-keyword="subsequence-array">subsequence sub of nums with length x is called valid if it satisfies:
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(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == … == (sub[x - 2] + sub[x - 1]) % 2.
Return the length of the longest valid subsequence of nums.
A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.
Example 1:
<div class="example-block"> Input: <span class="example-io">nums = [1,2,3,4]
Output: <span class="example-io">4
Explanation:
The longest valid subsequence is [1, 2, 3, 4].
Example 2:
<div class="example-block"> Input: <span class="example-io">nums = [1,2,1,1,2,1,2]
Output: 6
Explanation:
The longest valid subsequence is [1, 2, 1, 2, 1, 2].
Example 3:
<div class="example-block"> Input: <span class="example-io">nums = [1,3]
Output: <span class="example-io">2
Explanation:
The longest valid subsequence is [1, 3].
Constraints:
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2 ⇐ nums.length ⇐ 2 * 105 -
1 ⇐ nums[i] ⇐ 107