# algorithm

## Algorithm for graph homomorphisms ★★

Author(s): Fomin; Heggernes; Kratsch

**Question**

Is there an algorithm that decides, for input graphs and , whether there exists a homomorphism from to in time for some constant ?

Keywords: algorithm; Exponential-time algorithm; homomorphism

## Is there an algorithm to determine if a triangulated 4-manifold is combinatorially equivalent to the 4-sphere? ★★★

Author(s): Novikov

**Problem**Is there an algorithm which takes as input a triangulated 4-manifold, and determines whether or not this manifold is combinatorially equivalent to the 4-sphere?