Interview Question for Assistant Trader at Susquehanna International Group:

So, lets think of this as cycles of permutation [1,2,3,4,5]. So, [1,2,3,4,5] = [5,1,2,3,4] = [4,5,1,2,3]=[3,4,5,1,2]=[2,3,4,5,1]. As we can see, every permuation you find is in a equivalence relation with 4 other permuations. That means there are only 120/5 unique permuations, 5!/4 = 24

sorry 5!/5 = 24