Problem Statement

The Dutch national flag is composed of three coloured bands in the order:

The problem posed by Edsger Dijkstra is: When the problem was first posed, Dijkstra then went on to successively refine a solution, minimising the number of swaps and the number of times the colour of a ball needed to determined and restricting the balls to end in an array, ...

Let's start with the solution:

compare(a,b)={
  if (a==b,
    0
  ,
   if(a=="red" || b=="blue", -1, 1)
  )
};
r(n)=vector(n,i,if(random(3),if(random(2),"red","white"),"blue"));
inorder(v)=for(i=2,#v,if(compare(v[i-1],v[i])>0,return(0)));1;

v=r(10);
while(inorder(v), v=r(10));
v=vecsort(v,compare);
inorder(v)