题最早由E.W.Dijkstra所提出，他所使用的用语为Dutch Nation Flag（Dijkstra为荷兰人），而多数人会则使用Three-Color Flag来称之。

假设有一条绳子，上面有蓝、白、红三种颜色的旗子，起初绳子上的旗子颜色并没有顺序，您希望将之分类，并排列为蓝、白、红的顺序，要如何移动次数才会最少，注意您只能在绳子上进行这个动作，而且一次只能调换两个旗子。

-Tricolor problem was first raised by the EWDijkstra, the term he uses for the Dutch Nation Flag (Dijkstra is Dutch), but most people will use the Three-Color Flag to call it.

Suppose there is a rope above a blue, white and red colors of the flag, the color of the rope on the flag initially did not order, you want to classification and arrangement of blue, white and red of the order, how times before moving will be minimal, note that you can only perform this action on a rope, and one can only swap two flag.