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Grokking the Coding Interview Patterns in Python

Middle of the Linked List

Explore how to identify the middle node in a singly linked list by applying the fast and slow pointer method. Understand how to correctly return the second middle node when the list has an even number of nodes. Learn to approach this common linked list problem with an efficient, step-by-step technique.

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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.

Python
usercode > Solution.py
# Definition for a Linked List node

# class ListNode:

#     def __init__(self, val=0, next=None):

#         self.val = val

#         self.next = next

from ds_v1.LinkedList.LinkedList import ListNode



def get_middle_node(head):



    # Replace this placeholder return statement with your code

    return head
Middle of the Linked List