TopCoder problem "BunnyPuzzle" used in SRM 463 (Division II Level One)

Problem Statement

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Taro and Hanako are playing Bunny Puzzle. There are several bunnies standing on a line. You are given a int[] bunnies, where each element is the initial position of a single bunny.

They must perform the following routine exactly once:

Choose two different bunnies A and B, located at points a and b, respectively.
A jumps over B and lands at point 2*b-a.

The jump is not allowed if another bunny is already at point 2*b-a.

The jump is also not allowed if A jumps over more than one bunny.

Return the number of different ways in which Taro and Hanako can choose the pair of bunnies A and B. "A jumps over B" and "B jumps over A" are considered to be different.

Definition

Class:	BunnyPuzzle
Method:	theCount
Parameters:	int[]
Returns:	int
Method signature:	int theCount(int[] bunnies)
(be sure your method is public)

Constraints

bunnies will contain between 2 and 50 elements, inclusive.

Each element of bunnies will be between -10^6 and 10^6, inclusive.

bunnies will be sorted in strictly ascending order.

Examples

{5, 8}

Returns: 2

There are two possible moves:

A bunny jumps from 5 to 11
A bunny jumps from 8 to 2

{-1, 0, 1}

Returns: 2

There are two possible moves:

A bunny jumps from 0 to -2
A bunny jumps from 0 to 2

{0, 1, 3}

Returns: 3

There are three possible moves:

A bunny jumps from 0 to 2
A bunny jumps from 1 to -1
A bunny jumps from 1 to 5

{-677, -45, -2, 3, 8, 29, 384, 867}

Returns: 7

{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

Returns: 2

Problem url:

http://www.topcoder.com/stat?c=problem_statement&pm=10740

Problem stats url:

http://www.topcoder.com/tc?module=ProblemDetail&rd=14148&pm=10740

Writer:

rng_58

Testers:

PabloGilberto , misof , ivan_metelsky

Problem categories:

Simple Search, Iteration