middle-of-linked-list.js

/*
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.

*/


var middleNode = function(head) {
    let p1 = head
    let p2 = head 

    while(p2 && p2.next){
        p2 = p2.next.next
        p1 = p1.next
    }
    return p1
};

/*
initial state
f
1 -> 2 -> 3 -> 4 -> 
1st loop
		  f
1 -> 2 -> 3 -> 4 -> 5
     s
	 
2nd loop
		            f
1 -> 2 -> 3 -> 4 -> 5
          s
*/