UNO Gets Easier for a Single Player

This work is a follow up to[2, FUN 2010], which initiated a detailed analysis of the popular game of UNO®. We consider the solitaire version of the game, which was shown to be NP-complete. In[2], the authors also demonstrate a \(n^{O(c^2)}\) algorithm, where c is the number of colors across all the cards, which implies, in particular that the problem is polynomial time when the number of colors is a constant.