swap-nodes-in-pairs

java

python

python3

mysql

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oraclesql

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postgresql

Algorithms

Given a&nbsp;linked list, swap every two adjacent nodes and return its head. You must solve the problem without&nbsp;modifying the values in the list&#39;s nodes (i.e., only nodes themselves may be changed.)

&nbsp;
Example 1:

<div class="example-block">
Input: head = [1,2,3,4]

Output: [2,1,4,3]

Explanation:

<img alt="" src="https://assets.leetcode.com/uploads/2020/10/03/swap_ex1.jpg" style="width: 422px; height: 222px;" />
</div>

Example 2:

<div class="example-block">
Input: head = []

Output: []
</div>

Example 3:

<div class="example-block">
Input: head = [1]

Output: [1]
</div>

Example 4:

<div class="example-block">
Input: head = [1,2,3]

Output: [2,1,3]
</div>

&nbsp;
Constraints:

<ul>
	<li>The number of nodes in the&nbsp;list&nbsp;is in the range <code>[0, 100]</code>.</li>
	<li><code>0 &lt;= Node.val &lt;= 100</code></li>
</ul>