LC 30
Substring with Concatenation of All Words
Hard · LC 1–100
Candidate solution routes
Variable-Size Sliding Window
Invariant: left and right never retreat; whenever a result is recorded, the maintained state exactly matches [left,right] and satisfies the variant's validity or minimality condition.
candidate confidence: 0.510 · metadata_only
Fixed-Size Sliding Window
Invariant: After processing right endpoint r, the summary exactly describes the most recent at most k items; a result is recorded only at length k.
candidate confidence: 0.440 · metadata_only
Prefix State plus Hash Frequency
Invariant: Before processing position i, the table contains exactly the historical prefixes allowed as left boundaries; query-before-insert avoids using a future or self state accidentally.
candidate confidence: 0.368 · 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.