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Tighten the bound on the number of 4-contact placements to O(k n)

Establish whether, for a convex k-gon P and a convex n-gon Q in the plane (under general position), the number of similar copies of P contained in Q that have four distinct vertices of P in contact with the boundary of Q can be bounded by O(k n), improving the current O(k^4 n) upper bound.

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Background

The authors prove a near-linear-in-n combinatorial upper bound and an enumeration procedure for placements where four vertices of P are in contact with Q’s boundary (the 4-contact case), obtaining an O(k4 n) bound (up to logarithmic factors) under general position. This disproves a prior conjecture expecting Ω(k n2) such placements.

They explicitly ask whether this bound can be further tightened to O(k n), which would significantly improve the structural understanding of feasible 4-contact placements and potentially lead to faster algorithms.

References

The main question we leave open is whether Problem 1 can be solved in O(k n{1+ε}) time for all constant ε > 0, which would be a strict improvement over the previous O(k n2) bound for all k. Similarly, could the number of 4-contact placements of P within Q be upper-bounded by O(k n) instead of O(k4 n)?

Convex Polygon Containment: Improving Quadratic to Near Linear Time (2403.13292 - Chan et al., 20 Mar 2024) in Final Remarks