1582 articles
Merge k sorted linked lists into one sorted list using a min-heap for O(N log k) efficiency. Amazon uses this to test heap-based k-way merge, a critical pattern in distributed data systems.
Count the number of inversions in an array using a modified merge sort that counts cross-inversions during the merge step. Google tests this to evaluate divide-and-conquer mastery and algorithmic optimization under O(N log N) constraints.
Count contiguous subarrays whose elements sum to k using prefix sums and a frequency hashmap. Meta asks this to test prefix sum mastery and O(N) optimization over brute-force O(N^2) solutions.
Find the k most frequent elements in an array using a min-heap or bucket sort. Amazon asks this to test frequency counting, heap manipulation, and O(N) bucket sort optimization for bounded frequency ranges.
Return the rightmost visible node at each level of a binary tree using BFS level order traversal. Meta uses this to test BFS confidence, level tracking, and tree traversal variants applied to visual rendering problems.