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            "content": "<p>Given a <strong>non-empty</strong>&nbsp;array of integers <code>nums</code>, every element appears <em>twice</em> except for one. Find that single one.</p>\n\n<p>You must&nbsp;implement a solution with a linear runtime complexity and use&nbsp;only constant&nbsp;extra space.</p>\n\n<p>&nbsp;</p>\n<p><strong class=\"example\">Example 1:</strong></p>\n<pre><strong>Input:</strong> nums = [2,2,1]\n<strong>Output:</strong> 1\n</pre><p><strong class=\"example\">Example 2:</strong></p>\n<pre><strong>Input:</strong> nums = [4,1,2,1,2]\n<strong>Output:</strong> 4\n</pre><p><strong class=\"example\">Example 3:</strong></p>\n<pre><strong>Input:</strong> nums = [1]\n<strong>Output:</strong> 1\n</pre>\n<p>&nbsp;</p>\n<p><strong>Constraints:</strong></p>\n\n<ul>\n\t<li><code>1 &lt;= nums.length &lt;= 3 * 10<sup>4</sup></code></li>\n\t<li><code>-3 * 10<sup>4</sup> &lt;= nums[i] &lt;= 3 * 10<sup>4</sup></code></li>\n\t<li>Each element in the array appears twice except for one element which appears only once.</li>\n</ul>\n",
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