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25 lines
1.1 KiB
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<p>Given an integer array <code>nums</code> of length <code>n</code> where all the integers of <code>nums</code> are in the range <code>[1, n]</code> and each integer appears <strong>once</strong> or <strong>twice</strong>, return <em>an array of all the integers that appears <strong>twice</strong></em>.</p>
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<p>You must write an algorithm that runs in <code>O(n) </code>time and uses only constant extra space.</p>
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<p> </p>
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<p><strong>Example 1:</strong></p>
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<pre><strong>Input:</strong> nums = [4,3,2,7,8,2,3,1]
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<strong>Output:</strong> [2,3]
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</pre><p><strong>Example 2:</strong></p>
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<pre><strong>Input:</strong> nums = [1,1,2]
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<strong>Output:</strong> [1]
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</pre><p><strong>Example 3:</strong></p>
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<pre><strong>Input:</strong> nums = [1]
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<strong>Output:</strong> []
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li><code>n == nums.length</code></li>
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<li><code>1 <= n <= 10<sup>5</sup></code></li>
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<li><code>1 <= nums[i] <= n</code></li>
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<li>Each element in <code>nums</code> appears <strong>once</strong> or <strong>twice</strong>.</li>
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</ul>
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