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33 lines
1.3 KiB
HTML
33 lines
1.3 KiB
HTML
<p>Given the <code>head</code> of a linked list, reverse the nodes of the list <code>k</code> at a time, and return <em>the modified list</em>.</p>
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<p><code>k</code> 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 <code>k</code> then left-out nodes, in the end, should remain as it is.</p>
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<p>You may not alter the values in the list's nodes, only nodes themselves may be changed.</p>
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<p> </p>
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<p><strong class="example">Example 1:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/10/03/reverse_ex1.jpg" style="width: 542px; height: 222px;" />
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<pre>
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<strong>Input:</strong> head = [1,2,3,4,5], k = 2
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<strong>Output:</strong> [2,1,4,3,5]
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</pre>
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<p><strong class="example">Example 2:</strong></p>
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<img alt="" src="https://assets.leetcode.com/uploads/2020/10/03/reverse_ex2.jpg" style="width: 542px; height: 222px;" />
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<pre>
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<strong>Input:</strong> head = [1,2,3,4,5], k = 3
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<strong>Output:</strong> [3,2,1,4,5]
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</pre>
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<p> </p>
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<p><strong>Constraints:</strong></p>
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<ul>
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<li>The number of nodes in the list is <code>n</code>.</li>
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<li><code>1 <= k <= n <= 5000</code></li>
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<li><code>0 <= Node.val <= 1000</code></li>
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</ul>
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<p> </p>
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<p><strong>Follow-up:</strong> Can you solve the problem in <code>O(1)</code> extra memory space?</p>
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