CodeSignal Technical Assessment Core Data Structures 4

Question 1

Which data structure would you use to find the k-th largest element in a stream of numbers efficiently?

Accepted Answer

Min-heap of size k

Answer

A min-heap of size k keeps the k largest seen elements; its root is always the k-th largest.

Question 2

What is the time complexity of deleting a node from the middle of a singly linked list, given a pointer directly to that node?

Accepted Answer

O(1)

Answer

With a direct pointer, you can copy the next node's data into the current node and delete the next node in O(1) time.

Question 3

In a hash map using chaining, what is the worst-case time complexity for a lookup?

Accepted Answer

O(n)

Answer

If all n keys hash to the same bucket, the chain becomes a linked list of length n, requiring O(n) search.

Question 4

Which property distinguishes a complete binary tree from a full binary tree?

Accepted Answer

A complete binary tree fills all levels left-to-right with the last level possibly incomplete; a full binary tree has every node with exactly 0 or 2 children

Answer

Complete binary trees fill each level left to right (last level may be partial), while full binary trees require every node to have 0 or 2 children.

Question 5

What is a trie (prefix tree) primarily optimized for?

Accepted Answer

Fast prefix-based string lookups and autocomplete

Answer

A trie stores strings character by character, making prefix searches and autocomplete O(m) where m is the prefix length.

Codesignal Practice Test

Codesignal Practice Test

CodeSignal Technical Assessment Core Data Structures 4