remove-nth-node-from-end-of-list.js

// 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.


/**
 * 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 f(x) {
        if (x === null)
            return 0;
        var t = x.next;
        var tn = f(t);
        if (tn === n)
            x.next = t.next;

        return tn + 1;
    }
    if (f(head) === n)
        head = head.next;
    return head;
};