Solution to a hacker earth problem

race.rb

# Logic : first create list of all players and then remove loosers from that. Using a hash it can be done in O(n) time.

no_of_inputs = 2 ** gets.chomp.to_i - 1

player_list = Hash.new

inputs = [];

1.upto(no_of_inputs) do
	player1,player2 = gets.split(" ")
	inputs.push([player1, player2])
	player_list[player1] = player_list[player2] = 1
end

inputs.each do |input|
	player_list[input[1]] = -1
end

player_list.each do |player, state|
	print player if state == 1
end