Middle of the Linked List

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Problem

Given the head of a singly linked list, return the middle node of the linked list.

If there are two middle nodes, return the second middle node.

Example 1:

Input: head = [1,2,3,4,5]
Output: [3,4,5]
Explanation: The middle node of the list is node 3.

Example 2:

Input: head = [1,2,3,4,5,6]
Output: [4,5,6]
Explanation: Since the list has two middle nodes with values 3 and 4, we return the second one.

Pseudocode

traverse linked list and store each node in an array, return (length / 2) + 1 from array

fast and slow pointer
https://leetcode.com/problems/middle-of-the-linked-list/solutions/1651600/python-java-c-simple-solution-one-pass-beginner-friendly-detailed-explanation/

Solution

var middleNode = function(head) {
  let stack = []
  let cur = head

  while(cur) {
    stack.push(cur)
    cur = cur.next
  }

  let mid = Math.floor(stack.length / 2)

  return stack[mid]
}

Time and Space Complexity

Time

• Iterate through the linked list to find the length, return the middle node

• Total - O(N)

Space

• Stores all the nodes in array - O(N)

• Total - O(N)