19. Remove Nth Node From End of List
Given the head of a linked list, remove the nth node from the end of the list and return its head.
Example 1:
Input: head = [1,2,3,4,5], n = 2
Output: [1,2,3,5]
Example 2:
Input: head = [1], n = 1
Output: []
Example 3:
Input: head = [1,2], n = 1
Output: [1]
Constraints:
- The number of nodes in the list is sz.
- 1 <= sz <= 30
- 0 <= Node.val <= 100
- 1 <= n <= sz
Follow up: Could you do this in one pass?
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
ListNode first = head;
ListNode res = new ListNode(0);
res.next = head;
ListNode second = res;
while(first!=null){
first = first.next;
if(n--<=0){
second = second.next;
}
}
second.next = second.next.next;
return res.next;
}
}设置两个指针p,q，先让p指针走N步骤，然后p指针和q指针一起走，等p指针走到尾节点，删除q指针的next元素