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Grokking the Coding Interview Patterns in JavaScript

Middle of the Linked List

Explore how to use the fast and slow pointers technique to find the middle node in a singly linked list. Understand the approach for both odd and even numbers of nodes, and gain hands-on experience implementing an efficient solution.

We'll cover the following...

Statement

Given the head of a singly linked list, return the middle node of the linked list. If the number of nodes in the linked list is even, there will be two middle nodes, so return the second one.

Constraints:

Let n be the number of nodes in a linked list.

  • 1≤1 \leq n ≤100\leq 100
  • 1≤1 \leq Node.value ≤100\leq 100
  • head ≠\neq NULL

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

Middle of the Linked List

1.

What is the output if the following linked list is given as input?

2 → 4 → 6 → 8 → 10 → NULL

A.

4

B.

6

C.

2

D.

8

1 / 3

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4

Try it yourself

Implement your solution in the following coding playground.

JavaScript
usercode > Solution.js
// Definition for a Linked List node

// class ListNode {

//     constructor(val = 0, next = null) {

//         this.val = val;

//         this.next = next;

//     }

// }



import {ListNode} from './ds_v1/LinkedList.js';



function getMiddleNode(head){

    

    // Replace this placeholder return statement with your code

    return head;

}



export {

    getMiddleNode

};
Middle of the Linked List