HackerHeap

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

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.

Solution 1:

public class Solution {
    public ListNode removeNthFromEnd(ListNode head, int n) {
        if(head == null) return null;
        int count = 0;
        ListNode temp = head;
        ListNode returnNode = head;
        ListNode before = null;
        while(temp!=null){
            temp = temp.next;
            count++;
        }
        for(int i = 0;head!=null && i<count-n;i++){
            before = head;
            head = head.next;
        }
        if(returnNode == head){
            head = head.next;
            returnNode = head;
        }else{
        before.next = head.next;
        }
        return returnNode;
    }
}