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SRM29 Jan 2015
SRM 652

ThePermutationGameDiv2

Problem statement, definition, constraints, and public examples.

Problem Statement

Alice and Bob are playing a game called "The Permutation Game". The game is parameterized with the int N. At the start of the game, Alice chooses a positive integer x, and Bob chooses a permutation of the first N positive integers. Let p be Bob's permutation. Alice will start at 1, and apply the permutation to this value x times. More formally, let f(1) = p[1], and f(m) = p[f(m-1)] for all m >= 2. Alice's final value will be f(x). Alice wants to choose the smallest x such that f(x) = 1 for any permutation Bob can provide. Compute and return the value of such x.

Definition

Class:
ThePermutationGameDiv2
Method:
findMin
Parameters:
int
Returns:
long
Method signature:
long findMin(int N)
(be sure your method is public)

Notes

  • The return value will fit into a signed 64-bit integer.
  • A permutation of the first N positive integers is a sequence of length N that contains each of the integers 1 through N exactly once. The i-th (1-indexed) element of a permutation p is denoted by p[i].

Constraints

  • N will be between 1 and 35 inclusive.

Examples

  1. 2
    Returns: 2
    Bob can choose the permutations {1,2} or {2,1}. If Alice chooses 1, then, Bob can choose the permutation {2,1}, which would would make f(1) = 2. However, if Alice chooses 2, no matter which permutation Bob chooses, Alice will get f(2) = 1. Thus the answer in this case is 2.
  2. 3
    Returns: 6
  3. 6
    Returns: 60
  4. 11
    Returns: 27720
  5. 25
    Returns: 26771144400
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