LC 52
N-Queens II
Hard · LC 1–100
Candidate solution routes
Primary
FreeConstraint-satisfaction backtracking
Invariant: At recursion entry, the partial assignment satisfies every activated constraint and every auxiliary set/count exactly matches it; a pruned branch has no legal completion.
candidate confidence: 0.740 · metadata_only
How to use this page
Read the statement and constraints first, then validate recognition signals, invariant, and complexity. Candidate score is not correctness evidence.