Permutation game | HackerRank
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  1. Prepare
  2. Algorithms
  3. Game Theory
  4. Permutation game

Permutation game

Alice and Bob play the following game:

  1. They choose a permutation of the numbers to .
  2. Alice plays first and they alternate.
  3. In a turn, they can remove any one remaining number from the permutation.
  4. The game ends when the remaining numbers form an increasing sequence of or more numbers. The person who played the turn that leaves an increasing sequence wins the game.

Assuming both play optimally, who wins the game? Return Alice or Bob.

Example

This is the starting permutation to analyze, . First, Alice chooses or . For the example, Alice chooses and leaves . Since this is a decreasing sequence, Bob can remove any number for optimum play. He will lose regardless. Alice then removes any number leaving an array of only one element. Since Alice removed the last element to create an increasing sequence, Alice wins.

Function Description

Complete the permutationGame function in the editor below.

permutationGame has the following parameter:
- int arr[n]: the starting permutation

Returns

  • string: either Alice or Bob

Input Format

The first line contains the number of test cases .

Each of the next pairs of lines is in the following format:
- The first line contains an integer , the size of the array
- The second line contains space-separated integers, where

Constraints

  • The permutation will not be an increasing sequence initially.

Sample Input

STDIN       Function
-----       --------
2           t = 2
3           arr[] size n = 3
1 3 2       arr = [1, 3, 2]
5           n = 5
5 3 2 1 4   arr = [5, 3, 2, 1, 4]

Sample Output

Alice
Bob

Explanation

For the first test, Alice can remove or to leave an increasing sequence and win the game.

For the second test, if is removed then the only way to have an increasing sequence is to only have number left. This takes a total of moves, and Bob wins.

If Alice removes the on the first move, it will take more moves to create an increasing sequence. Bob wins. If Alice removes something else, Bob can remove on his next turn to create the same game state. It is a decreasing sequence with numbers left.