# Find the position u of first repetition. mu = 0 tortoise = x0 while tortoise != hare: tortoise = f(tortoise) hare = f(hare) # Hare and tortoise move at same speed mu += 1 # Find the length of the shortest cycle starting from x_u # The hare moves one step at a time while tortoise is still. # lam is incremented until ? is found. lam = 1 hare = f(tortoise) while tortoise != hare: hare = f(hare) lam += 1 return lam, mu

This code only accesses the sequence by storing