LeetCode short: edge cases

A new YouTube Short argues candidates miss LeetCode 2452 on rule handling, not algorithm choice: compare positions, count mismatches, stop at two. (youtube.com) LeetCode 2452 is called “Words Within Two Edits of Dictionary.” The task asks whether each query word can match any dictionary word after changing at most two letters, and LeetCode says all words are lowercase and the same length. (leetcode.com) That same-length rule turns the problem into a position-by-position check, not full edit distance with insertions and deletions. The Short says many people reach for dynamic programming anyway, even though its stated shortcut is to count character mismatches and stop early once the count passes two. (youtube.com) Reference solutions published by LeetCode explain the same core idea: compare each query against each dictionary word and keep the query if some pair differs in at most two positions. Community writeups list the time cost as checking query count × dictionary count × word length. (leetcode.com) (leetcode.doocs.org) The edge cases are where interview answers usually break. A query with exactly two mismatches should pass, a query with three should fail, and a query should be added once even if several dictionary words qualify. (leetcode.com) (algo.monster) The Short packages that into interview advice: restate the rules before coding and enumerate boundary cases before writing loops. In this problem, that means saying out loud that “edit” only means replacing letters, because the input length never changes. (youtube.com) That distinction matters because many string problems do use the broader edit-distance model, where insertion, deletion, and substitution all count. LeetCode 2452 does not; its official statement defines one edit as changing one letter to another letter. (leetcode.com) The clip’s “90% get this wrong” framing is a YouTube title, not a published LeetCode statistic. But the example it uses matches a common interview failure mode: solving a harder problem than the one on the screen. (youtube.com) So the clean solution is also the literal one: read the constraints, compare aligned characters, and treat “at most two” as the rule that decides every branch. (leetcode.com)