ds-algo-study/DS-n-Algos/_Extra-Practice/fromlast/index.js

Just experimenting with publishing a package

// --- Directions
// Given a linked list and integer n, return the element n
// spaces from the last node in the list.  Do not call the
// 'size' method of the linked list.  Assume that n will always
// be less than the length of the list.
// --- Examples
//    const list = new List();
//    list.insertLast('a');
//    list.insertLast('b');
//    list.insertLast('c');
//    list.insertLast('d');
//    fromLast(list, 2).data // 'b'

function fromLast(list, n) {
  let slow = list.getFirst();
  let fast = list.getFirst();

  while (n > 0) {
    fast = fast.next;
    n--;
  }

  while (fast.next) {
    slow = slow.next;
    fast = fast.next;
  }

  return slow;
}

module.exports = fromLast;