Backtracking Interview Questions & Solutions

Backtracking is how you enumerate possibilities without drowning in them. You build a solution one choice at a time, and the instant a partial solution can't possibly work you abandon it — undo the last choice and try the next. It's brute force made disciplined, and it's the pattern behind permutations, combinations, subsets, and every "find all valid arrangements" puzzle interviewers reach for.

The solutions here make the universal template explicit: choose, explore (recurse), un-choose. Once you see that skeleton, generating subsets, permutations, and combinations becomes almost mechanical, and the harder constraint problems — N-Queens, word search, sudoku-style grids, palindrome partitioning — are the same skeleton with a smarter "is this still valid?" check. We pay special attention to pruning, because the difference between an elegant backtracking solution and one that times out is usually a single well-placed early exit. Learn to recognize the "generate all / find all" phrasing and you'll know to reach for this pattern immediately.