I Almost Failed This Coding Interview (Backtracking Gone Wrong)
Watch a real mock coding interview where a simple backtracking problem turns into a 20-minute struggle to convert the right idea into working code. This is the kind of honest, unpolished interview footage that actually prepares you for what coding rounds feel like.
The interview covers the Letter Combinations of a Phone Number problem — a classic backtracking question where you map digit inputs to all possible letter combinations. The candidate immediately identifies the correct approach (recursive backtracking) but gets tangled mixing iterative and recursive logic, needs multiple hints to separate the two, and has to rethink the recursion structure mid-interview. The interviewer walks through targeted feedback at the end, covering what passed, what needed work, and whether this performance would advance to the next round.
0:00 Problem introduction: Letter combinations of a phone number
1:15 Identifying the backtracking approach
2:30 Setting up the digit-to-letter mapping
5:10 First attempt at recursive implementation
7:30 Getting stuck mixing iterative and recursive logic
10:09 Interviewer hint: separating the two approaches
12:17 Reworking the backtracking structure
15:50 Debugging the index progression
18:00 Cleaning up the recursive calls
22:14 Final solution walkthrough
22:32 Interviewer feedback: what passed and what didn't
24:40 Verdict: would this advance to the next round?
25:20 Tip: preserving test cases across code changes