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SRM22 Nov 2011
SRM 529

MinskyMystery

Problem statement, definition, constraints, and public examples.

Problem Statement

Marvin plays a simple game. The game is played with an infinite supply of marbles and five bags, labeled "bag 0" through "bag 4".

At the beginning, Marvin takes N marbles (where N is a nonnegative integer) and places them into bag 0. The remaining four bags are left empty. Marvin then follows this simple algorithm:

    Add a marble into bag 1.
    Repeat forever:
        Add a marble into bag 1.
        Empty bag 4.
        While there are marbles in bag 0:
            While there are marbles both in bag 0 and in bag 1:
                Remove a marble from bag 0.
                Remove a marble from bag 1.
                Add a marble into bag 2.
                Add a marble into bag 3.
            End While
            Add a marble into bag 4.
            If bags 0 and 1 are both empty:
                Move all marbles from bag 3 to bag 4.
                TERMINATE THE GAME
            End If
            Move all marbles from bag 3 to bag 1.
        End While
        Move all marbles from bag 2 to bag 0.
    End Repeat

You are given a long N. Count the number of times a marble enters a bag during Marvin's game. That is, compute X+Y, where X is the number of times a marble is added to some bag, and Y is the number of times a marble is moved from one bag to another. To avoid overflows, return just the value ((X+Y) modulo 1,000,000,009). If Marvin's game does not terminate for the given N, return -1 instead.

Definition

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

Notes

  • Suppose there are M marbles in bag A. The instruction "Move all marbles from bag A to bag B." then counts as M individual moves.
  • Note that N is allowed to be zero.

Constraints

  • N will be between 0 and 10^12, inclusive.

Examples

  1. 2
    Returns: 9
  2. 3
    Returns: 27
  3. 4
    Returns: 16
  4. 2401
    Returns: 59058
  5. 24
    Returns: 86
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