19-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 currNode = head;
    let nodeBeforeN = head;

    for (let i = 0; i < n; i++) {
        currNode = currNode.next;
    }

    if (!currNode) {
        return head.next;
    }

    while (currNode.next) {
        nodeBeforeN = nodeBeforeN.next;
        currNode = currNode.next;
    }

    nodeBeforeN.next = nodeBeforeN.next.next;

    return head;
};