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HackerRank's Interview Preparation Kit plus the highest-signal practice problems companies still pull from HackerRank assessments.
About this plan
HackerRank powers a huge share of first-round online assessments, and its Interview Preparation Kit is the closest thing to the company's own answer key. This 150-problem set expands that kit with the most-asked array, hashmap, greedy, DP, graph, and tree problems on the platform — the ones that actually show up in timed OAs.
Each problem links to an InterviewExplainer walkthrough in the same brute-force → optimal, line-by-line Java and Python format. Problems not yet written show as "Queued"; the list is stable so your progress is never lost as walkthroughs land.
Why this sheet
How to use it
The problem set
The Interview Prep Kit's gentle on-ramp.
1-D and 2-D array manipulation.
O(1) lookup problems.
Comparison sorts and counting sort.
Parsing and transformation.
Locally optimal choices.
Binary search and BFS/DFS variants.
Memoization and tabulation.
LIFO/FIFO design.
BFS, DFS, shortest path.
Traversals and BST.
Pointer manipulation.
Divide and conquer.
Bit tricks, time complexity, and number theory.
Keep exploring