Remove Nth Node From End of List_Leetcode_#19

1.题目

Given a linked list, remove the nth node from the end of list and return its head.

For example,

Given linked list: 1->2->3->4->5, and n = 2.

After removing the second node from the end, the linked list becomes 1->2->3->5.

Note:

Given n will always be valid.

Try to do this in one pass.

2.解法

思路：快慢指针

时间复杂度：O(N)

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode removeNthFromEnd(ListNode head, int n) {
// 2 pointers
ListNode start = new ListNode(0);
ListNode slow = start, fast = start;
slow.next = head;

for(int i = 0; i <= n; i++){
fast = fast.next;
}
while(fast != null){
slow = slow.next;
fast = fast.next;
}
slow.next = slow.next.next;
return start.next;
}
}