Unique Binary Search Trees

Invariant: dfs(u,parent) returns the exact optimum for every boundary mode of u's subtree. Distinct child subtrees interact only through u and can therefore be folded independently.

candidate confidence: 0.675 · metadata_only

Invariant: At node entry, (low,high) is the intersection of all ancestor constraints; a legal value lies inside it. In inorder form, every visited value is greater than the previous one.

candidate confidence: 0.740 · metadata_only