leetcode hot 11

合集 - leetcode hot100(25)

1.leetcode hot 0102-152.leetcode hot 0202-153.leetcode hot 0402-164.leetcode hot 0302-155.leetcode hot 0502-176.leetcode hot 0602-197.leetcode hot 0702-208.leetcode hot 0802-219.leetcode hot 0902-2110.leetcode hot 1002-2411.leetcode hot 1202-2512.leetcode hot 1302-2613.leetcode hot 1402-2814.leetcode hot 1503-01

15.leetcode hot 1103-03

16.leetcode hot 1603-0317.leetcode hot 1703-0318.leetcode hot 1803-0319.leetcode hot 1903-0420.leetcode hot 2003-0521.leetcode hot 2103-0522.leetcode hot 2203-1223.leetcode hot 2303-1224.leetcode hot 2403-1225.leetcode hot 2503-12

收起

解题思路:熟能生巧，链表问题就是用指针来模拟，链表反转很经典，利用三个指针，两个指着head，一个指着null，然后模拟。

/**
 * 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) {
        if(head==null) return head;
        ListNode pre = null;
        ListNode cur = head;
        ListNode next = head;
        while(cur!=null){
            next = cur.next;
            cur.next = pre;
            pre = cur;
            cur = next;
        }
        return pre;
    }
}