111 lines
3.0 KiB
Java
111 lines
3.0 KiB
Java
/*
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* The MIT License (MIT)
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*
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* Copyright © 2021 xrv <xrg@live.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package io.github.ehlxr.datastructure.linkedlist;
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/**
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* @author ehlxr
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* @since 2021-12-23 14:40.
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*/
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public class ReverseLinkedList {
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public static void main(String[] args) {
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ListNode n5 = new ListNode(5, null);
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ListNode n4 = new ListNode(4, n5);
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ListNode n3 = new ListNode(3, n4);
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ListNode n2 = new ListNode(2, n3);
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ListNode n1 = new ListNode(1, n2);
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ListNode head = new ListNode(0, n1);
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print(head);
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System.out.println("-------------");
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// head = reverse(head);
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head = reverse2(head);
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// head = reverse3(head, null);
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print(head);
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}
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public static void print(ListNode head) {
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if (head == null) {
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return;
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}
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ListNode n = head;
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while (n != null) {
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System.out.println(n);
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n = n.getNext();
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}
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}
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// 循环方式
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public static ListNode reverse(ListNode head) {
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if (head == null || head.getNext() == null) {
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return head;
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}
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ListNode pre = null;
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ListNode cur = head;
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while (cur != null) {
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ListNode next = cur.getNext();
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cur.setNext(pre);
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pre = cur;
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cur = next;
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}
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return pre;
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}
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// 递归一
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public static ListNode reverse2(ListNode head) {
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if (head == null || head.getNext() == null) {
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return head;
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}
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ListNode next = head.getNext();
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ListNode node = reverse2(next);
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head.getNext().setNext(head);
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head.setNext(null);
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return node;
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}
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// 递归二
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public static ListNode reverse3(ListNode head, ListNode pre) {
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if (head == null) {
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return pre;
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}
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ListNode next = head.getNext();
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ListNode node = reverse3(next, head);
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head.setNext(pre);
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return node;
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}
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}
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