Is Linked List Components easy or hard?

Linked List Components is considered a medium-level problem on LeetCode with an acceptance rate around 58%. The challenge lies in recognizing component boundaries and using a hash set to avoid repeated membership scans.

Linked List Components Python/Java solution

Python and Java solutions typically build a HashSet or set from nums and iterate through the linked list. When a node is in the set and the next node is not, increment the component count. This implementation runs in O(n) time and is the standard interview solution.

How to solve Linked List Components in O(n)?

Insert all values from nums into a hash set. Traverse the linked list and check if the current node value is in the set while the next node value is not. Each such boundary marks the end of a component, so increment the counter. Because each node is processed once, the total complexity is linear.

What is the best approach for Linked List Components?

The most efficient approach uses a hash set to store all values from nums and then traverses the linked list once. When a node value is in the set and the next node is not, you count a component boundary. This runs in O(n) time with O(k) extra space, where k is the size of nums.

Is Linked List Components asked at Google/Amazon/Meta?

Linked list and hash set combination problems appear frequently in interviews at companies like Amazon, Google, and Meta. This problem tests recognition of connected segments and efficient membership lookup using hashing.

What data structure is used in Linked List Components?

The primary data structure used is a hash set for constant-time membership checks. The problem also requires traversal of a singly linked list and understanding how consecutive nodes form components.

What is the time complexity of Linked List Components?

The optimal solution runs in O(n + k) time, where n is the number of nodes in the linked list and k is the size of nums. Each node is visited once and set membership checks take O(1) on average.

Description Solution Video 5:20

817. Linked List Components

Medium58.4% acceptance4 companies

You are given the head of a linked list containing unique integer values and an integer array nums that is a subset of the linked list values.

Return the number of connected components in nums where two values are connected if they appear consecutively in the linked list.

Example 1:

Input: head = [0,1,2,3], nums = [0,1,3]
Output: 2
Explanation: 0 and 1 are connected, so [0, 1] and [3] are the two connected components.

Example 2:

Input: head = [0,1,2,3,4], nums = [0,3,1,4]
Output: 2
Explanation: 0 and 1 are connected, 3 and 4 are connected, so [0, 1] and [3, 4] are the two connected components.

Constraints: