Reverse a Linked List Coding Interview Question | Skilled.dev
Interview Question

Reverse a Linked List

Write a function reverseLinkedList that takes a head node of a singly linked list, reverses it in place, and returns the new head node.

You will be given the head as the input, and you should return the new head for the reverse linked list which is the current tail node. All the items should be in reverse order, starting with the tail (new head). The reverse should happen in place which means you should not create a new linked list.

class Node {
  constructor(data) {
    this.data = data;
    this.next = null;
  }
}

// Input
const head = new Node(42); // ... then add more nodes
42 -> 52 -> 4 -> 6 -> 1 -> 9000

// Output
9000 -> 1 -> 6 -> 4 -> 52 -> 42

Breakdown

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Validate My Answer

  1. You only need to iterate through the list once which means it will be O(n) time.

  2. You will need three pointers to store nodes and no additional data structures. This will be O(1) space.

  3. The solution doesn't use a lot of code, but it does require writing the procedure carefully and in the correct order. Make sure you handle this and think through edge cases.

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Test Results

Run your code and see results here...

const reverseLinkedList = (head) => {
  // Your solution here
};
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Reverse a Linked List

Write a function reverseLinkedList that takes a head node of a singly linked list, reverses it in place, and returns the new head node.

You will be given the head as the input, and you should return the new head for the reverse linked list which is the current tail node. All the items should be in reverse order, starting with the tail (new head). The reverse should happen in place which means you should not create a new linked list.

class Node {
  constructor(data) {
    this.data = data;
    this.next = null;
  }
}

// Input
const head = new Node(42); // ... then add more nodes
42 -> 52 -> 4 -> 6 -> 1 -> 9000

// Output
9000 -> 1 -> 6 -> 4 -> 52 -> 42
const reverseLinkedList = (head) => {
  // Your solution here
};
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// Upgrade for full course access