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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.

Ten small programs, each one producing a real error that disappears without a log, a stack trace or a non-zero exit code, with the measured output that proves it and the rule or line that finally made it visible.

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.

The XOR and popcount tricks behind Single Number, Missing Number and Counting Bits are small enough to verify exhaustively, so this runs them over every input they claim to cover and reports the exact value at which each one stops being correct.

Runes look like function calls but compile into signals, proxies and effects, so the fastest way to understand them is to read what svelte/compiler emits for each one.

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.