Largest Rectangle in Histogram: A Step-by-Step Interview Walkthrough
Largest Rectangle in Histogram earns its status as a hard problem because while the brute force solution is obvious, the optimization is not, and the leap between them requires a genuinely clever data structure: the monotonic stack.
1 day ago16 min read
Median of Two Sorted Arrays: A Step-by-Step Interview Walkthrough
Median of Two Sorted Arrays is one of the most famous Hard problems in the interview canon, and its reputation is earned by a single, brutal constraint: the required time complexity is O(log(m + n)). Without that constraint, the problem is trivial — merge the two arrays and grab the middle. With it, you're forced into a binary search, except there's no obvious single sorted array to binary-search over.
3 days ago16 min read
Minimum Window Substring: A Step-by-Step Interview Walkthrough
Minimum Window Substring is the problem that separates people who've used sliding windows from people who understand them. Most candidates have seen a window expand and contract on simpler problems, but this one forces two harder questions at once: how do you efficiently check whether the current window contains everything you need (including duplicates), and how do you know when to expand versus when to shrink?
5 days ago15 min read
