題目
Given the head
of a linked list, remove the nth
node from the end of the list and return its head.
A mapping of digit to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
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]
思路
用左右雙指針,先將右邊移動直到雙方相差 n
,再讓左右同時移動直到右邊到底為止,這時左邊就會是後面數來第n
個。
Solution
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* @param {ListNode} head
* @param {number} n
* @return {ListNode}
*/
var removeNthFromEnd = function(head, n) {
var h = new ListNode(0)
var l = h
var r = h
h.next = head
for (var i = 0; i < n + 1; i++) {
r = r.next
}
while(r !== null) {
l = l.next
r = r.next
}
l.next = l.next.next
return h.next
};
Complexity
- Time complexity : O(n)
- Space complexity : O(1)