Project Notes

Find the Duplicate Number

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Description

tab: English
 
<p>Given an array of integers <code>nums</code> containing&nbsp;<code>n + 1</code> integers where each integer is in the range <code>[1, n]</code> inclusive.</p>
 
<p>There is only <strong>one repeated number</strong> in <code>nums</code>, return <em>this&nbsp;repeated&nbsp;number</em>.</p>
 
<p>You must solve the problem <strong>without</strong> modifying the array <code>nums</code>&nbsp;and using only constant extra space.</p>
 
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
 
<pre>
<strong>Input:</strong> nums = [1,3,4,2,2]
<strong>Output:</strong> 2
</pre>
 
<p><strong class="example">Example 2:</strong></p>
 
<pre>
<strong>Input:</strong> nums = [3,1,3,4,2]
<strong>Output:</strong> 3
</pre>
 
<p><strong class="example">Example 3:</strong></p>
 
<pre>
<strong>Input:</strong> nums = [3,3,3,3,3]
<strong>Output:</strong> 3</pre>
 
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
 
<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>nums.length == n + 1</code></li>
	<li><code>1 &lt;= nums[i] &lt;= n</code></li>
	<li>All the integers in <code>nums</code> appear only <strong>once</strong> except for <strong>precisely one integer</strong> which appears <strong>two or more</strong> times.</li>
</ul>
 
<p>&nbsp;</p>
<p><b>Follow up:</b></p>
 
<ul>
	<li>How can we prove that at least one duplicate number must exist in <code>nums</code>?</li>
	<li>Can you solve the problem in linear runtime complexity?</li>
</ul>
 
 
 
---
 
[submissions](https://leetcode.com/problems/find-the-duplicate-number/submissions/) | [solutions](https://leetcode.com/problems/find-the-duplicate-number/solutions/)
 
 
tab: 中文
 
<p>给定一个包含&nbsp;<code>n + 1</code> 个整数的数组&nbsp;<code>nums</code> ，其数字都在&nbsp;<code>[1, n]</code>&nbsp;范围内（包括 <code>1</code> 和 <code>n</code>），可知至少存在一个重复的整数。</p>
 
<p>假设 <code>nums</code> 只有 <strong>一个重复的整数</strong> ，返回&nbsp;<strong>这个重复的数</strong> 。</p>
 
<p>你设计的解决方案必须 <strong>不修改</strong> 数组 <code>nums</code> 且只用常量级 <code>O(1)</code> 的额外空间。</p>
 
<p>&nbsp;</p>
 
<p><strong>示例 1：</strong></p>
 
<pre>
<strong>输入：</strong>nums = [1,3,4,2,2]
<strong>输出：</strong>2
</pre>
 
<p><strong>示例 2：</strong></p>
 
<pre>
<strong>输入：</strong>nums = [3,1,3,4,2]
<strong>输出：</strong>3
</pre>
 
<p><strong>示例 3 :</strong></p>
 
<pre>
<strong>输入：</strong>nums = [3,3,3,3,3]
<strong>输出：</strong>3
</pre>
 
<p>&nbsp;</p>
 
<p>&nbsp;</p>
 
<p><strong>提示：</strong></p>
 
<ul>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>nums.length == n + 1</code></li>
	<li><code>1 &lt;= nums[i] &lt;= n</code></li>
	<li><code>nums</code> 中 <strong>只有一个整数</strong> 出现 <strong>两次或多次</strong> ，其余整数均只出现 <strong>一次</strong></li>
</ul>
 
<p>&nbsp;</p>
 
<p><b>进阶：</b></p>
 
<ul>
	<li>如何证明 <code>nums</code> 中至少存在一个重复的数字?</li>
	<li>你可以设计一个线性级时间复杂度 <code>O(n)</code> 的解决方案吗？</li>
</ul>
 
 
 
---
 
[提交记录](https://leetcode.cn/problems/find-the-duplicate-number/submissions/) | [题解](https://leetcode.cn/problems/find-the-duplicate-number/solution/)

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