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

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} head
 * @param {number} n
 * @return {ListNode}
 */
var removeNthFromEnd = function(head, n) {
    let fast = head, slow = head
    for (let i = 0; i < n; i++) fast = fast.next
    if (!fast) return head.next
    while (fast.next) fast = fast.next, slow = slow.next
    slow.next = slow.next.next
    return head
};