Linked Lists - Length & Count

Problom §

Description:
 
Linked Lists - Length & Count
 
Implement Length() to count the number of nodes in a linked list.
 
length(null) === 0
length(1 -> 2 -> 3 -> null) === 3
Implement Count() to count the occurrences of an integer in a linked list.
 
count(null, 1) === 0
count(1 -> 2 -> 3 -> null, 1) === 1
count(1 -> 1 -> 1 -> 2 -> 2 -> 2 -> 2 -> 3 -> 3 -> null, 2) === 4
I've decided to bundle these two functions within the same Kata since they are both very similar.
 
The push() and buildOneTwoThree() functions do not need to be redefined.

linked List의 길이와 데이터를 구하는 문제. 어렵지 않은 문제라고 생각했으나 best 답변을 보니 생각보다 머리를 굴릴 요소가 많았다.

My Solution §

function Node(data) {
  this.data = data;
  this.next = null;
}
 
function length(head) {
  var count = 0;
  while(head) {
    count++;
    head = head.next;
  }
  return count;
}
 
function count(head, data) {
  var count = 0;
  while(head) {
    if (head.data === data) {
      count++;
    }
    head = head.next;
  }
  return count;
}

Best Solution §

function Node(data) {
  this.data = data
  this.next = null
}
 
function length(head) {
  return head ? 1 + length(head.next) : 0
}
 
function count(head, data) {
  if (!head) return 0
  return (head.data === data ? 1 : 0) + count(head.next, data)
}

굉장히 우아하게 답을 구했다. 리커시브가 옳은 경우인듯? 나중에 누구한테 리커시브 설명해 줄 일이 있으면 링크드 리스트의 길이를 구하는 문제를 보여주면 될 거 같다.