LeetCode video: Letter combos
A new LeetCode tutorial on 'Letter Combinations of a Phone Number' surfaced and highlights recursive backtracking and real‑world variants that Big Tech likes to twist in interviews posted. The video emphasizes pattern recognition, modular code structure, and thinking through edge cases — core skills for timed coding rounds.
LeetCode's problem page leetcode.com lists this as Problem #17 (Medium), enforces 1 ≤ digits.length ≤ 4, and shows 2,944,097 accepted submissions with a 65.6% acceptance rate. The standard time complexity is O(n·4^n) with worst-case branching from digits like '7' and '9', and common analyses report space on the order of O(4^n) for the result set. walkccc.me Iterative BFS/queue solutions are a frequent alternative to recursion — GeeksforGeeks documents an iterative queue approach that extends prefixes per digit — while tutorials catalog four canonical approaches (brute-force loops, backtracking/DFS, BFS/queue, and optimized iterative). geeksforgeeks.org Interview-tracking summaries and community writeups show this exact prompt appearing at major firms: an aggregated dev.to listing tallies Amazon (5), Google (5), Microsoft (6) and Facebook/Meta (4) occurrences, and a DestinationFAANG video marks it as asked at Google, Amazon, Meta and Microsoft. dev.to Real‑world variants frequently surface in interviews: several walkthroughs and guides describe adding a dictionary constraint and checking generated strings against a Trie to return only valid English words (a common follow‑up in product‑style questions). geeksforgeeks.org Canonical solutions emphasize in‑place push/pop or StringBuilder mutation to avoid shared‑state bugs and explicit empty‑input handling (returning []), patterns shown in NeetCode's writeup and multiple reference repos that include Python, C++ and Java examples. neetcode.io
