On the complexity of some coloring games

In this paper we consider the following game: players must alternately color the lowest numbered uncolored vertex of a given graph G= ({1, 2,…, n}, E) with a color, taken from a given set C, such that two adjacent vertices are never colored with the same color. In one variant, the first player which is unable to move, loses the game. In another variant, player 1 wins the game if and only if the game ends with all vertices colored. We show that for both variants, the problem of determining whether there is a winning strategy for player 1 is PSPACE-complete for any C with |C|≥3, but the problems are solvable in , and time, respectively, if |C|=2. We also give polynomial time algorithms for the problems with certain restrictions on the graphs and orderings of the vertices. We give some partial results for the versions where no order for coloring the vertices is specified.