206.反转链表

力扣题目链接(opens new window)

题意：反转一个单链表。

示例: 输入: 1->2->3->4->5->NULL 输出: 5->4->3->2->1->NULL

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode reverseList(ListNode head) {

        //保存还没有进行反转的链表
        ListNode temp = null;

        // cur表示当前的结点
        ListNode cur = head;

        //pre表示已经反转的链表
        ListNode pre = null;


        while (cur != null) {

            temp = cur.next;
            cur.next = pre;
            pre = cur;
            cur = temp;

        }

        return pre;


    }
}