Rock Paper Scissors
I had a test for my comp sci class and one of the questions was to make a rock paper scissors game, if winner 1 won, it would return -1, if player won 2, it would return 1. and if it was a draw it would return 0. I did my program and ran and it worked, but according to my professor, he said it wasn't.
def rps(x,y):
player1 = -1
player2 = 1
tie = 0
'R'>'S'
'P'>'R'
'S'>'P'
if x>y:
return player1
if x<y:
return player2
else:
return tie
I don't see what's wrong with that? If you do rps ("R", "P") then it will return -1 because x = player1 and because Rock hits Paper. Can anyone help me find out if my code is wrong?
There are several problems in your code:
1. The following lines do nothing. You cannot set a character R
greater than a character S
:
'R' > 'S'
'P' > 'R'
'S' > 'P'
2. Reason for section 1, yours if x>y:
doesn't do what you think. It just checks if the content is x
before the content y
in the alphabet. (Assume content x
and y
are characters)
Your code is difficult to fix, I would recommend that you approach this problem from a completely different angle.
The solution here is completely different from yours, but it works. It just uses a lot of checks if
to get the result.
def rps(p1, p2):
if p1 == p2:
return 0
elif (p1 == "R" and p2 == "S")\
or (p1 == "S" and p2 == "P")\
or (p1 == "P" and p2 == "R"):
return -1
else:
return 1
I replaced x, y
with p1, p2
as they represent the best player options, but if you need to use x
and y
, just change them.
You can follow these steps:
def rps(p1,p2):
retval= {
'R':{'R': 0, 'S':-1, 'P': 1},
'S':{'R': 1, 'S': 0, 'P':-1},
'P':{'R':-1, 'S': 1, 'P': 0}
}
return retval[p1][p2]
You asked:
Can someone help me see if my code is wrong?
Yes, it’s wrong. That's why.
If you run rps('R','S')
, you should get 1
it because rock beats paper. Likewise, I rps('R','P')
have to give -1
, because paper hits rock. They both work in your code.
However, if you run rps('S','P')
, you should get 1
because the scissors hit the paper, but you don't - your code returns -1
, which is wrong.
As Emumi pointed out in the comments, three lines
'R'>'S'
'P'>'R'
'S'>'P'
which I assume you think is the defining application to use, is not really doing anything.
def rps(x,y):
return [0, -1, 1]['RPS'.index(x) - 'RPS'.index(y)]
Or if you want an interactive program:
from random import randint
['Tie', 'I win', 'You win'][randint(0, 2) - 'RPS'.index(raw_input("Enter R, P, or S: "))]
def rps(x,y):
d = {'R': 1, 'S': 2, 'P': 3}
return ((d[x] - d[y]) + 1) % 3 - 1
for p1 in 'RPS':
for p2 in 'RPS':
print p1, p2, rps(p1, p2)
prints
R R 0
R P 1
R S -1
P R -1
P P 0
P S 1
S R 1
S P -1
S S 0