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.
4 days 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.
6 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?
Jun 2015 min read
