Simple rock, paper, scissors game - ruby

Question

I wrote a "Rock, paper, scissors" game:
puts "Hello, this is a rock, papers, scissors game. Let's play."
puts "Player 1, plase enter your choice: \n"
puts "r for rock. \np for paper. \ns for scissors."
p1 = gets.chomp.downcase
puts "Player 2, please enter your choice: \n"
puts "r for rock. \np for paper. \ns for scissors."
p2 = gets.chomp.downcase
if p1 == 'r' && p2 == 's'
puts "Player 1 wins."
elsif p1 == 'r' && p2 == 'p'
puts "Player 2 wins."
elsif p1 == 'r' && p2 == 'r'
puts "Tie."
elsif p1 == 'p' && p2 == 'r'
puts "Player 1 wins."
elsif p1 == 'p' && p2 == 's'
puts "Player 2 wins."
elsif p1 == 'p' && p2 == 'p'
puts "Tie."
elsif p1 == 's' && p2 == 'r'
puts "Player 2 wins."
elsif p1 == 's' && p2 == 'p'
puts "Player 1 wins."
elsif p1 == 's' && p2 == 's'
puts "Tie."
end
It works, however, that's a lot of elsifs, and I know that this is possible with case...when statements, the thing is that I can't figure out how.
I was trying to use a return statement depending on the input: "return 0 for rock, 1 for paper and 2 for scissors", and then use a conditional to say something like "hey, if player one returns 1 and player 2 also returns 1, then puts 'tie'", and the same for the other possible results.
I was trying to associate a number to the result: return - 1 when player one wins, return 0 for a tie, and return 2 for player two wins.
I did it like this, but it's kind of the same, and I feel that it's so bad:
case p1
when p1 == 'r' && p2 == 'r'
result = 0
when p1 == 'r' && p2 == 'p'
result = 1
when p1 == 'r' && p2 == 's'
result = -1
when p1 == 'p' && p2 == 'r'
result = -1
when p1 == 'p' && p2 == 'p'
result = 0
when p1 == 'p' && p2 == 's'
result = 1
when p1 == 's' && p2 == 'r'
result = 1
when p1 == 's' && p2 == 'p'
result = -1
when p1 == 's' && p2 == 's'
result = 0
end
if result == -1
puts "P1 wins"
elsif result == 0
puts "Tie"
elsif result == 1
puts "P2 wins"
end
I would appreciate any kind of help.

Answer 1

An array can be used as a ring, with each item having
a weaker item to its right, and a stronger one to its left.
weapons = ['paper', 'rock', 'scissors']
select weapons by your favorite means
w1 = weapons[rand(weapons.length)]
w2 = weapons[rand(weapons.length)]
rotate array till w1 is at the center
while weapons[1] != w1
weapons.rotate! 1
end
now the result is indicated by the index of w2 in weapons array, conveniently.
verbs = ['is beat by', 'ties', 'beats']
puts "#{w1} #{verbs[weapons.index(w2)]} #{w2}"
Example output from a few runs:
paper beats rock
paper ties paper
rock beats scissors
scissors beats paper
rock is beat by paper
You could get creative and add a hash of verb-arrays, one for each weapon, using w1 as the key so that it would output (for example) paper covers rock, etc.

Answer 2

You can try something like this :
if (p1 == p2)
puts "Tie"
elsif (p1 == 'r' && p2 == 'p') ||
(p1 == 'p' && p2 == 's') ||
(p1 == 's' && p2 == 'r')
puts "P2 wins"
else
puts "P1 wins"
end

Answer 3

You could also do the ruby equivalent of saying
If p1 = 'r' then
goto R
endif
If p1 = 'p' then
goto S
endif
etc.
then at your goto locations later
R:
if p2 = 'r' then
puts "tie"
etc.
however the idea of p1 = p2 then ... is a good one.

Answer 4

Here's another way:
WINNERS = {s: :p, p: :r, r: :s}
# => {:s=>:p, :p=>:r, :r=>:s}
def win_lose_or_tie?(me, you)
return "I win! :-)" if WINNERS[me] == you
return "you win! :-(" if WINNERS[you] == me
"it's a tie :-|"
end
keys = WINNERS.keys
keys.product(keys).each { |me, you|
puts "If I play #{me} and you play #{you}, then #{win_lose_or_tie?(me, you)}" }
# If I play s and you play s, then it's a tie :-|
# If I play s and you play p, then I win! :-)
# If I play s and you play r, then you win! :-(
# If I play p and you play s, then you win! :-(
# If I play p and you play p, then it's a tie :-|
# If I play p and you play r, then I win! :-)
# If I play r and you play s, then I win! :-)
# If I play r and you play p, then you win! :-(
# If I play r and you play r, then it's a tie :-|

Answer 5

I'd use a case/when statement like:
result = case [p1, p2]
when %w[r r], %w[p p], %w[s s]
0
when %w[r p], %w[p s], %w[s r]
1
when %w[r s], %w[p r], %w[s p]
-1
end
puts case result
when 0
"Tie"
when -1
"P1 wins"
when 1
"P2 wins"
end
But, after writing that this makes more sense:
puts case [p1, p2]
when %w[r r], %w[p p], %w[s s]
'Tie'
when %w[r p], %w[p s], %w[s r]
'P1 wins'
when %w[r s], %w[p r], %w[s p]
'P2 wins'
end
Here's a test:
[
%w[r r], %w[p p], %w[s s],
%w[r p], %w[p s], %w[s r],
%w[r s], %w[p r], %w[s p]
].each do |p1, p2|
puts case [p1, p2]
when %w[r r], %w[p p], %w[s s]
'Tie'
when %w[r p], %w[p s], %w[s r]
'P1 wins'
when %w[r s], %w[p r], %w[s p]
'P2 wins'
end
end
# >> Tie
# >> Tie
# >> Tie
# >> P1 wins
# >> P1 wins
# >> P1 wins
# >> P2 wins
# >> P2 wins
# >> P2 wins