reverse-nodes-in-k-group.md

<p>Given a linked list, reverse the nodes of a linked list <em>k</em> at a time and return its modified list.</p>

<p><em>k</em> is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of <em>k</em> then left-out nodes in the end should remain as it is.</p>

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<p><strong>Example:</strong></p>

<p>Given this linked list: <code>1-&gt;2-&gt;3-&gt;4-&gt;5</code></p>

<p>For <em>k</em> = 2, you should return: <code>2-&gt;1-&gt;4-&gt;3-&gt;5</code></p>

<p>For <em>k</em> = 3, you should return: <code>3-&gt;2-&gt;1-&gt;4-&gt;5</code></p>

<p><strong>Note:</strong></p>

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	<li>Only constant extra memory is allowed.</li>
	<li>You may not alter the values in the list&#39;s nodes, only nodes itself may be changed.</li>
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