Remove Nth Node From End of List

Description

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.

Note:

Given n will always be valid.

Follow up:

Could you do this in one pass?

Solution(javascript)

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
    function getNode(h, m) {
        var rst = h;
        while(m > 0) {
            rst = rst.next;
            m--;
        }
        return rst;
    }
    
    var l = head;
    var r = getNode(head, n);
    if (!r) return head.next;
    
    while(r.next) {
        r = r.next;
        l = l.next;
    }
    l.next = l.next.next;
    
    return head;
};