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| 1 | +<h2><a href="https://leetcode.com/problems/find-the-maximum-length-of-valid-subsequence-i">Find the Maximum Length of Valid Subsequence I</a></h2> <img src='https://img.shields.io/badge/Difficulty-Medium-orange' alt='Difficulty: Medium' /><hr>You are given an integer array <code>nums</code>. |
| 2 | +<p>A <span data-keyword="subsequence-array">subsequence</span> <code>sub</code> of <code>nums</code> with length <code>x</code> is called <strong>valid</strong> if it satisfies:</p> |
| 3 | + |
| 4 | +<ul> |
| 5 | + <li><code>(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == ... == (sub[x - 2] + sub[x - 1]) % 2.</code></li> |
| 6 | +</ul> |
| 7 | + |
| 8 | +<p>Return the length of the <strong>longest</strong> <strong>valid</strong> subsequence of <code>nums</code>.</p> |
| 9 | + |
| 10 | +<p>A <strong>subsequence</strong> is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.</p> |
| 11 | + |
| 12 | +<p> </p> |
| 13 | +<p><strong class="example">Example 1:</strong></p> |
| 14 | + |
| 15 | +<div class="example-block"> |
| 16 | +<p><strong>Input:</strong> <span class="example-io">nums = [1,2,3,4]</span></p> |
| 17 | + |
| 18 | +<p><strong>Output:</strong> <span class="example-io">4</span></p> |
| 19 | + |
| 20 | +<p><strong>Explanation:</strong></p> |
| 21 | + |
| 22 | +<p>The longest valid subsequence is <code>[1, 2, 3, 4]</code>.</p> |
| 23 | +</div> |
| 24 | + |
| 25 | +<p><strong class="example">Example 2:</strong></p> |
| 26 | + |
| 27 | +<div class="example-block"> |
| 28 | +<p><strong>Input:</strong> <span class="example-io">nums = [1,2,1,1,2,1,2]</span></p> |
| 29 | + |
| 30 | +<p><strong>Output:</strong> 6</p> |
| 31 | + |
| 32 | +<p><strong>Explanation:</strong></p> |
| 33 | + |
| 34 | +<p>The longest valid subsequence is <code>[1, 2, 1, 2, 1, 2]</code>.</p> |
| 35 | +</div> |
| 36 | + |
| 37 | +<p><strong class="example">Example 3:</strong></p> |
| 38 | + |
| 39 | +<div class="example-block"> |
| 40 | +<p><strong>Input:</strong> <span class="example-io">nums = [1,3]</span></p> |
| 41 | + |
| 42 | +<p><strong>Output:</strong> <span class="example-io">2</span></p> |
| 43 | + |
| 44 | +<p><strong>Explanation:</strong></p> |
| 45 | + |
| 46 | +<p>The longest valid subsequence is <code>[1, 3]</code>.</p> |
| 47 | +</div> |
| 48 | + |
| 49 | +<p> </p> |
| 50 | +<p><strong>Constraints:</strong></p> |
| 51 | + |
| 52 | +<ul> |
| 53 | + <li><code>2 <= nums.length <= 2 * 10<sup>5</sup></code></li> |
| 54 | + <li><code>1 <= nums[i] <= 10<sup>7</sup></code></li> |
| 55 | +</ul> |
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