Bowling calculator - ruby

Question

I am writing a bowling score calculator in Ruby that is defined and tested using RSpec. It currently runs, but only passes 5 of the 8 input tests. Here is the code for my implementation:
class ScoreKeeper
def calculate(input)
unless input.is_a? String
raise argumentException, "Score Keeper will only except string types for score calculation."
end
# Thanksgiving Turkey Edge Case
return 300 if input == "xxxxxxxxxxxx"
# Calculate Score
throws = input.gsub(/-/, "0").split(//)
score = 0
throws.each_with_index do |ball, i|
current_throw = i
last_throw = throws[i - 1] || "0"
lastlast_throw = throws[i - 2] || "0"
next_throw = throws[i + 1] || "0"
if current_throw == 0
last_throw = 0
lastlast_throw = 0
end
if current_throw == 1
lastlast_throw = 0
end
working_value = 0
# Add numbers directly (unless part of a spare frame)
if ((1..9) === ball.to_i)
working_value = ball.to_i
end
# Add strike as 10 points
if ball == "x"
working_value = 10
end
# Add spare as number of remaining pins from last throw
if ball == "/"
if last_throw == "/" || last_throw == "x"
raise argumentException, "Invalid score string. A spare cannot immediately follow a strike or spare."
end
working_value = 10 - last_throw.to_i
end
# Strike / Spare Bonus
if last_throw == "x" || last_throw == "/" || lastlast_throw == "x"
score += working_value
end
# Add current throw value
score += working_value
end
if score > 300 || score < 0
raise argumentExcpetion, "Invalid score string. Impossible score detected."
end
score
end
end
I can't tell why my code is not calculating a proper score in every test case.
The RSpec:
require "./score_keeper"
describe ScoreKeeper do
describe "calculating score" do
let(:score_keeper) { described_class.new }
context "when rolls are valid" do
{
"xxxxxxxxxxxx" => 300,
"--------------------" => 0,
"9-9-9-9-9-9-9-9-9-9-" => 90,
"5/5/5/5/5/5/5/5/5/5/5" => 150,
"14456/5/---17/6/--2/6" => 82,
"9/3561368153258-7181" => 86,
"9-3/613/815/0/8-7/8-" => 121,
"x3/61xxx2/9-7/xxx" => 193
}.each do |bowling_stats, score|
it "returns #{score} for #{bowling_stats}" do
expect(score_keeper.calculate(bowling_stats)).to eq score
end
end
end
end
end
The failing inputs are:
"5/5/5/5/5/5/5/5/5/5/5" (expected: 150, got: 155),
"x3/61xxx2/9-7/xxx" (expected: 82, got: 88),
"14456/5/---17/6/--2/6" (expected: 193, got: 223)

Answer 1

The first thing I see is your use of gsub:
input.gsub(/-/, "0")
You're not assigning the string returned by gsub to anything, and instead you're throwing it away.
input = '#0#'
input.gsub('0', '-') # => "#-#"
input # => "#0#"
I suspect you're thinking of the mutating gsub! but instead I suggest simply passing the value to split:
_frames = input.gsub(/-/, "0").split(//)
Your code is not idiomatic Ruby; There are a number of things you need to do differently:
Instead of if !input.is_a? String use:
unless input.is_a? String
raise argumentException, "Score Keeper will only except string types for score calculation."
end
It's considered better to use unless than a negated test.
Instead of
if input == "xxxxxxxxxxxx"
return 300
end
use a "trailing if":
return 300 if input == "xxxxxxxxxxxx"
Don't name variables with a leading _. _frames should be frames.
Don't name variables like lastFrame, lastlastFrame and workingValue with mixed-case AKA "camelCase". We use "snake_case" for Ruby variables and methods and camelCase for classes and modules. It_is_a matterOfReadability.
Don't end lines with a trailing ;:
workingValue = 0;
The only time we use a trailing semicolon is when we're using multiple statements on a single line, which should be extremely rare. Just don't do that unless you know why and when you should.
Consider the potential problem you have here:
"12".include?('1') # => true
"12".include?('2') # => true
"12".include?('12') # => true
While your code might skirt that issue, don't write code like that and think about side-effects. Perhaps you want to really test to see if the value is an integer between 1 and 9?
((1 .. 9) === '1'.to_i) # => true
((1 .. 9) === '2'.to_i) # => true
((1 .. 9) === '12'.to_i) # => false
Instead of using
return score
you can simply use
score
Ruby will return the last value seen; You don't have to explicitly return it.
Indent your code properly. Your future self will appreciate it when you have to dive back into code to debug something. Consistenly use two space indents.
Use whitespace liberally to separate your code into readable blocks. It doesn't affect the run-time speed of your code and it makes it a lot easier to read. Again, your future self will appreciate it.
While it might seem nit-picking, those little things go a long way when coding in a team of developers, and failing to do those things can land you in the hot seat during a code-review.

Answer 2

You're problem appears to be that that for your first two frames you're adding the last two frames. Consider the following.
arr = [1,2,3,4,5,6,7,8,9]
arr.each_with_index do |num, i|
puts "current number #{num}"
puts arr[i-1]
puts arr[i-2]
end
I think you need an if statement to handle the first two frames because - index will loop back to the end of the array if you're at 0 index.
so you need something like
arr = [1,2,3,4,5,6,7,8,9]
arr.each_with_index do |num, i|
puts "current number #{num}"
if i <= 1
puts "no previous frame"
elsif i == 1
puts arr[i-1] + "can be added to frame 2"
else
puts arr[i-1] + "can be added to frame 1"
puts arr[i-2] + "can be added to frame 2"
end
end