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Delete the `if (!numSet.has(num - 1))` guard from the standard LeetCode 128 solution and every test still passes, but the inner loop jumps from 31,999 iterations to 511,984,000 at n = 32,000.

LeetCode 621 has two unrelated correct solutions — a heap simulation and a one-line formula — so running them against every task multiset up to size 14 crossed with every cooldown from 0 to 40 is a stronger test than any example you would write by hand.

Collapsing the 0/1 knapsack DP table into a single array is taught as a free win, but it destroys the record of which items were chosen and introduces a loop-direction bug that returns a plausible wrong answer on roughly four instances in five.

Bucket sort is O(n) and a size-k min-heap is O(n log k), but timing both on two million integers shows the comparison is decided by how many buckets you allocate rather than by k.

Nearly every explanation of LeetCode 84 says the monotonic stack stays strictly increasing, and an assertion dropped into the loop shows that is false on 45,502 of 50,000 random histograms.

Four rate limiting algorithms, one request stream, and a harness that counts what each of them actually admits in the worst rolling second.

LeetCode 56 merges [1,4] and [4,5]; LeetCode 435 says they do not overlap at all. Closed versus half-open ends is the one real decision in interval problems, and most interval bugs come from never making it.

Dijkstra's algorithm is four lines of greedy logic wrapped in machinery that fails quietly, so this post builds a binary-heap implementation in TypeScript, differential-tests it against Floyd-Warshall on 4,000 random graphs, and measures what the heap, the Array.shift() queue and the stale-entry check actually cost.