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data/problems/367.yml

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---
: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"