LC 24
Swap Nodes in Pairs
Medium · LC 1–100
Candidate solution routes
Primary
FreeLinked-List Pointer Rewiring
Invariant: prev bounds the correctly processed chain and cur is the first unprocessed node; every original node belongs to exactly one side and remains reachable.
candidate confidence: 0.613 · metadata_only
Alternate 1
FreeOpposite-Direction Two Pointers
Invariant: Every uneliminated pair uses endpoints inside [l,r]; a moved endpoint is proven unable to pair with any remaining opposite endpoint to satisfy the goal.
candidate confidence: 0.410 · 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.