LintCode List Remove Nth Node From End of List
25 Dec 2015###Task1 Given a linked list, remove the nth node from the end of list and return its head.
Have you met this question in a real interview? Yes Example Given linked list: 1->2->3->4->5->null, and n = 2.
After removing the second node from the end, the linked list becomes 1->2->3->5->null. Note The minimum number of nodes in list is n.
Challenge O(n) time
###java
/**
* Definition for ListNode.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int val) {
* this.val = val;
* this.next = null;
* }
* }
*/
public class Solution {
/**
* @param head: The first node of linked list.
* @param n: An integer.
* @return: The head of linked list.
*/
ListNode removeNthFromEnd(ListNode head, int n) {
// write your code here
if (head == null || n < 1) {
return null;
}
ListNode fast = head.next;
while (n > 0 && fast != null) {
fast = fast.next;
n--;
}
if (fast == null) {
return head.next;
}
ListNode itr = head;
while (fast != null) {
itr = itr.next;
fast = fast.next;
}
itr.next = itr.next.next;
return head;
}
}
###Points
- The case when to delete the first node: fast will be null!