Java单链逆转

本文介绍两种方法单向链表反转。记录，如下面：

1.

package com.leetcode;

public class ListReverse {

	public static void main(String[] args) {
		Node node1 = new Node(1);
		Node node2 = new Node(2);
		Node node3 = new Node(3);
		Node node4 = new Node(4);
		node1.next = node2;
		node2.next = node3;
		node3.next = node4;

		Node head = reverse(node1);
		while(head != null){
			System.out.println(head.val);
			head = head.next;
		}

	}

	public static Node reverse(Node head){
		Node cur = head, post = head.next;
		head.next = null;
		while(post != null){
			Node tmp = post;
			post = post.next;
			tmp.next = cur;
			cur = tmp;
		}
		return cur;
	}

	static class Node{
		int val;
		Node next;
		Node(int val){
			this.val = val;
			this.next = null;
		}
	}

}

执行结果为：

4
3
2
1

2.

package com.leetcode;

public class ListReverse {

	public static void main(String[] args) {
		Node node1 = new Node(1);
		Node node2 = new Node(2);
		Node node3 = new Node(3);
		Node node4 = new Node(4);
		node1.next = node2;
		node2.next = node3;
		node3.next = node4;

		Node head = reverse(node1);
		while(head != null){
			System.out.println(head.val);
			head = head.next;
		}

	}

	public static Node reverse(Node head){
		Node dummy = new Node(-1);
		dummy.next = head;
		Node pre = dummy, cur = head, post = head.next;
		while(post != null){
			cur.next = post.next;
			post.next = pre.next;
			pre.next = post;
			post = cur.next;
		}
		return dummy.next;
	}

	static class Node{
		int val;
		Node next;
		Node(int val){
			this.val = val;
			this.next = null;
		}
	}

}

执行结果为：

4
3
2
1

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