LeetCode 19. Remove Nth Node From End of List
LeetCode 19. Remove Nth Node From End of List (删除链表的倒数第 N 个结点)
题目
链接
https://leetcode-cn.com/problems/remove-nth-node-from-end-of-list/
问题描述
给你一个链表,删除链表的倒数第 n 个结点,并且返回链表的头结点。
示例
输入:head = [1,2,3,4,5], n = 2
输出:[1,2,3,5]
提示
链表中结点的数目为 sz
1 <= sz <= 30
0 <= Node.val <= 100
1 <= n <= sz
思路
快慢指针,同时slow初始值为pre的值,确保删除的结点刚好是倒数第n个点。
复杂度分析
时间复杂度 O(L)
空间复杂度 O(1)
代码
Java
public ListNode removeNthFromEnd(ListNode head, int n) {
ListNode pre = new ListNode();
pre.next = head;
ListNode fast = head;
ListNode slow = pre;
for (int i = 0; i < n; i++) {
fast = fast.next;
}
while (fast != null) {
fast = fast.next;
slow = slow.next;
}
slow.next = slow.next.next;
return pre.next;
}