edit distance

Palantir's bread and butter: 'Acme Corp.' and 'ACME Corporation, Inc.' are the same customer; prove it in code. Normalization does more work than the clever algorithm, and blocking is what makes it run before the heat death of the universe.

A DP classic that screens for one thing: can you define the right subproblem and fill the table without fumbling the indices. The strong version adds the O(min(m,n)) space trick and reconstructs the actual edits when the follow-up lands.