divide-array-into-equal-pairs

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Algorithms

You are given an integer array <code>nums</code> consisting of <code>2 * n</code> integers.

You need to divide <code>nums</code> into <code>n</code> pairs such that:

<ul>
	<li>Each element belongs to exactly one pair.</li>
	<li>The elements present in a pair are equal.</li>
</ul>

Return <code>true</code> if nums can be divided into <code>n</code> pairs, otherwise return <code>false</code>.

&nbsp;
Example 1:

<pre>
Input: nums = [3,2,3,2,2,2]
Output: true
Explanation: 
There are 6 elements in nums, so they should be divided into 6 / 2 = 3 pairs.
If nums is divided into the pairs (2, 2), (3, 3), and (2, 2), it will satisfy all the conditions.
</pre>

Example 2:

<pre>
Input: nums = [1,2,3,4]
Output: false
Explanation: 
There is no way to divide nums into 4 / 2 = 2 pairs such that the pairs satisfy every condition.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>nums.length == 2 * n</code></li>
	<li><code>1 &lt;= n &lt;= 500</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 500</code></li>
</ul>

divideArray

Divide Array Into Equal Pairs

Sort Array by Increasing Frequency

sort-array-by-increasing-frequency

按照频率将数组升序排序

Distribute Elements Into Two Arrays I

distribute-elements-into-two-arrays-i

将元素分配到两个数组中 I

Distribute Elements Into Two Arrays II

distribute-elements-into-two-arrays-ii

将元素分配到两个数组中 II

Bit Manipulation

Array

Hash Table

Counting

给你一个整数数组&nbsp;<code>nums</code>&nbsp;，它包含&nbsp;<code>2 * n</code>&nbsp;个整数。

你需要将&nbsp;<code>nums</code> 划分成&nbsp;<code>n</code>&nbsp;个数对，满足：

<ul>
	<li>每个元素 只属于一个 数对。</li>
	<li>同一数对中的元素 相等&nbsp;。</li>
</ul>

如果可以将 <code>nums</code>&nbsp;划分成 <code>n</code>&nbsp;个数对，请你返回 <code>true</code>&nbsp;，否则返回 <code>false</code>&nbsp;。

&nbsp;

示例 1：

<pre>
输入：nums = [3,2,3,2,2,2]
输出：true
解释：
nums<code>&nbsp;中总共有 6 个元素，所以它们应该被划分成</code> 6 / 2 = 3 个数对。
nums 可以划分成 (2, 2) ，(3, 3) 和 (2, 2) ，满足所有要求。
</pre>

示例 2：

<pre>
输入：nums = [1,2,3,4]
输出：false
解释：
无法将 nums 划分成 4 / 2 = 2 个数对且满足所有要求。
</pre>

&nbsp;

提示：

<ul>
	<li><code>nums.length == 2 * n</code></li>
	<li><code>1 &lt;= n &lt;= 500</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 500</code></li>
</ul>