1582 articles
Implement a HashSet from scratch using either a bit array for dense integer keys or chaining for general keys — the implementation-level interview that tests your understanding of set data structures.
Pick a uniformly random index of a target value without pre-processing, using reservoir sampling — an elegant streaming algorithm that appears in Google and Facebook interviews on probability and distributed systems.
LC 819 Most Common Word finds the most frequent non-banned word in a paragraph using normalization, regex tokenization, and a frequency hash map — a practical string-processing problem tested at Amazon and Microsoft.
LC 846 Hand of Straights asks whether cards can be rearranged into groups of consecutive values using a greedy frequency map — a FAANG-tested pattern that also appears in interval scheduling and task scheduling problems.
LC 974 Subarray Sum Divisible by K counts subarrays whose sum is divisible by K using prefix remainders and a frequency hash map — the canonical prefix mod pattern tested at Google, Amazon, and Facebook.