【入门】单双链表及其反转

单链表结点及链表反转

// 单链表节点
	public static class ListNode {
		public int val;
		public ListNode next;

		public ListNode(int val) {
			this.val = val;
		}

		public ListNode(int val, ListNode next) {
			this.val = val;
			this.next = next;
		}
	}

	// 反转单链表测试链接 : https://leetcode.cn/problems/reverse-linked-list/
	class Solution {
		public static ListNode reverseList(ListNode head) {
			ListNode pre = null;
			ListNode next = null;
			while (head != null) {
				next = head.next;
				head.next = pre;
				pre = head;
				head = next;
			}
			return pre;
		}
	}

双链表结点及链表反转

// 双链表节点
	public static class DoubleListNode {
		public int value;
		public DoubleListNode last;
		public DoubleListNode next;

		public DoubleListNode(int v) {
			value = v;
		}
	}

	// 反转双链表
	// 如下方法是对的
	public static DoubleListNode reverseDoubleList(DoubleListNode head) {
		DoubleListNode pre = null;
		DoubleListNode next = null;
		while (head != null) {
			next = head.next;
			head.next = pre;
			head.last = next;
			pre = head;
			head = next;
		}
		return pre;
	}