data/problems/367.yml
---
:id: 367
:name: Bozo sort
:url: https://projecteuler.net/problem=367
:content: " **Bozo sort** , not to be confused with the slightly less efficient **bogo
sort** , consists out of checking if the input sequence is sorted and if not swapping
randomly two elements. This is repeated until eventually the sequence is sorted.\n\nIf
we consider all permutations of the first 4 natural numbers as input the expectation
value of the number of swaps, averaged over all 4! input sequences is 24.75. \nThe
already sorted sequence takes 0 steps.\n\nIn this problem we consider the following
variant on bozo sort. \nIf the sequence is not in order we pick three elements
at random and shuffle these three elements randomly. \nAll 3!=6 permutations of
those three elements are equally likely. \nThe already sorted sequence will take
0 steps. \nIf we consider all permutations of the first 4 natural numbers as input
the expectation value of the number of shuffles, averaged over all 4! input sequences
is 27.5. \nConsider as input sequences the permutations of the first 11 natural
numbers. \nAveraged over all 11! input sequences, what is the expected number of
shuffles this sorting algorithm will perform?\n\nGive your answer rounded to the
nearest integer.\n\n"