2019-11-02 12:07:41 +08:00
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# 22. 链表中倒数第 K 个结点
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[NowCoder](https://www.nowcoder.com/practice/529d3ae5a407492994ad2a246518148a?tpId=13&tqId=11167&tPage=1&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking&from=cyc_github)
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## 解题思路
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设链表的长度为 N。设置两个指针 P1 和 P2，先让 P1 移动 K 个节点，则还有 N - K 个节点可以移动。此时让 P1 和 P2 同时移动，可以知道当 P1 移动到链表结尾时，P2 移动到第 N - K 个节点处，该位置就是倒数第 K 个节点。
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2019-12-06 10:11:23 +08:00
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<div align="center"> <img src="https://cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com/6b504f1f-bf76-4aab-a146-a9c7a58c2029.png" width="500"/> </div><br>
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2019-11-02 12:07:41 +08:00
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```java
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public ListNode FindKthToTail(ListNode head, int k) {
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if (head == null)
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return null;
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ListNode P1 = head;
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while (P1 != null && k-- > 0)
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P1 = P1.next;
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if (k > 0)
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return null;
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ListNode P2 = head;
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while (P1 != null) {
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P1 = P1.next;
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P2 = P2.next;
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}
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return P2;
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}
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```
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