https://dmytros.blog/tags/first-missing-positive/ Recent content in First Missing Positive on Dmytro's Blog https://dmytros.blog/images/papermod-cover.png https://dmytros.blog/images/papermod-cover.png Hugo -- 0.147.1 en Sat, 29 Aug 2026 17:57:45 +0300 https://dmytros.blog/posts/leetcode-first-missing-positive/ Sat, 29 Aug 2026 17:57:45 +0300 https://dmytros.blog/posts/leetcode-first-missing-positive/ <h3 id="the-problem">The problem</h3> <p>Given an unsorted integer array <code>nums</code>. Return the <em>smallest positive integer</em> that is <em>not present</em> in <code>nums</code>.</p> <p>You must implement an algorithm that runs in <code>O(n)</code> time and uses <code>O(1)</code> auxiliary space.</p> <p><strong>Example 1:</strong></p> <pre tabindex="0"><code>Input: nums = [1,2,0] Output: 3 Explanation: The numbers in the range [1,2] are all in the array. </code></pre><p><strong>Example 2:</strong></p> <pre tabindex="0"><code>Input: nums = [3,4,-1,1] Output: 2 Explanation: 1 is in the array but 2 is missing. </code></pre><p><strong>Example 3:</strong></p>