LeetCode: Middle of the Linked List Solution

Approach: Calculate Length

Calculate list length

Iterate to the middle

Implementation

1var middleNode = function (head) {
2  let n = 0
3
4  let iter = head
5  while (iter) {
6    n++
7    iter = iter.next
8  }
9
10  let mid = Math.floor(n / 2)
11  iter = head
12  while (mid--) {
13    iter = iter.next
14  }
15
16  return iter
17}

Approach: Fast and Slow

Slow pointer go 1 step, in the same time fast pointer go 2 steps

Implementation

1var middleNode = function (head) {
2  for (var slow = (fast = head); fast && fast.next; ) {
3    slow = slow.next
4    fast = fast.next.next
5  }
6
7  return slow
8}