1582 articles
Find the smallest window in s containing all characters of t using have/need counters and a frequency map. The canonical hard sliding-window problem asked at every top tech company.
Find the maximum in every sliding window of size k in O(n) using a monotonic decreasing deque of indices — the classic hard problem that separates senior engineers from the rest.
Find the shortest subarray whose sum is at least k, even with negative numbers, using a monotone increasing deque on prefix sums — the canonical hard problem where a simple sliding window fails.
Find the longest substring containing at most 2 distinct characters using a variable sliding window backed by a character frequency map — a premium LinkedIn and Google problem with a clean generalization to k distinct.
Find the longest contiguous subarray of 1s after deleting exactly one element. Reframe as "longest window with at most one zero," then subtract 1 for the mandatory deletion. A clean shrinkable window problem.