#!/usr/bin/env ruby
# Russian roulette simulation, by Kimmo Kulovesi <http://arkku.com/>

num_simulations = 100000
max_players = 10
num_chambers = 6
each_player_spins = false

2.upto(max_players) do |num_players|
    print "#{num_players} players"
    print ' (' + (each_player_spins ? 'each' : 'first') + ' spins)'
    $stdout.flush
    wins = 0
    num_simulations.times do
        first_alive = true
        players_left = num_players
        while first_alive and players_left > 1
            bullet_index = rand(num_chambers) + 1
            current_player = 0
            current_index = 0
            while bullet_index != current_index
                current_player += 1
                current_player = 1 if current_player > players_left
                if each_player_spins
                    current_index = rand(num_chambers) + 1
                else
                    current_index += 1
                end
            end
            first_alive = (current_player != 1)
            players_left -= 1
        end
        wins += 1 if first_alive
    end
    print ": #{wins} wins out of #{num_simulations}"
    print " -> #{wins.to_f / num_simulations}\n"
end