Trapping Rain Water

Invariant: Stack indexes increase, their values are monotone in the chosen direction, and every stored index has not yet encountered a right-side item that resolves it.

candidate confidence: 0.700 · metadata_only

Invariant: After each input prefix, frames from bottom to top are exactly the unfinished contexts in opening order, and the top is the only context directly affected next.

candidate confidence: 0.488 · metadata_only

Invariant: After processing i, every state through i equals the true value under its definition, and every future transition reads only these finalized states.

candidate confidence: 0.470 · metadata_only