## Discussion Forum

Que. | In a permutation a1.....an of n distinct integers, an inversion is a pair (ai, aj) such that i < j and ai > aj. If all permutations are equally likely, what is the expected number of inversions in a randomly chosen permutation of 1.....n ? |

a. | n(n - 1)/2 |

b. | n(n - 1)/4 |

c. | n(n + 1)/4 |

d. | 2n[log2 n] |

Answer:n(n - 1)/4 |