Sync LeetCode submission Runtime - 139 ms (19.38%), Memory - 39.1 MB (54.26%)

Author: jimit105

3490-find-the-maximum-length-of-valid-subsequence-i/README.md

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+You are given an integer array <code>nums</code>.
+<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>
+
+<ul>
+	<li><code>(sub[0] + sub[1]) % 2 == (sub[1] + sub[2]) % 2 == ... == (sub[x - 2] + sub[x - 1]) % 2.</code></li>
+</ul>
+
+<p>Return the length of the <strong>longest</strong> <strong>valid</strong> subsequence of <code>nums</code>.</p>
+
+<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>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [1,2,3,4]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">4</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>The longest valid subsequence is <code>[1, 2, 3, 4]</code>.</p>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [1,2,1,1,2,1,2]</span></p>
+
+<p><strong>Output:</strong> 6</p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>The longest valid subsequence is <code>[1, 2, 1, 2, 1, 2]</code>.</p>
+</div>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [1,3]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">2</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<p>The longest valid subsequence is <code>[1, 3]</code>.</p>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= nums.length &lt;= 2 * 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>7</sup></code></li>
+</ul>

3490-find-the-maximum-length-of-valid-subsequence-i/solution.py

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+# Approach: Parity of Enumeration Elements
+
+# Time: O(n)
+# Space: O(1)
+
+class Solution:
+    def maximumLength(self, nums: List[int]) -> int:
+        res = 0
+        for pattern in [(0, 0), (0, 1), (1, 0), (1, 1)]:
+            cnt = 0
+            for num in nums:
+                if num % 2 == pattern[cnt % 2]:
+                    cnt += 1
+            res = max(res, cnt)
+
+        return res
+