CODEWITHSUNDEEP
ruby
thefonso
thefonso

Reputation: 3390

pythagorean triangle with any side equal to zero

So I have this spec I'm trying to solve for (I did not write the spec)...

  it "returns false if any of the arguments are 0" do
    # [0, 1, 1].permutation(3) returns all permutations of [0, 1, 1]
    length = rand(0.01..100.0)
    [0, length, length].permutation(3).all? { |(a,b,c)| valid_triangle?(a,b,c) }.should be_false
  end

Here is my code

def valid_triangle?(a, b, c)
#A Pythagorean triple consists of three positive integers a, b, and c, such that a2 + b2 = c2.
  if a > 0 && b > 0 && c > 0
    one   = a**2
    two   = b**2
    three = c**2
    if one+two=three
      return "true"
    else
      return "false"
    end
  else
    return "false"
  end
end

How can I pass my spec? What am I missing?

Upvotes: 1

Views: 198

Answers (2)

Cary Swoveland
Cary Swoveland

Reputation: 110675

The main problem is that when the test permutes the values of a, b and c, your method is not always checking that it is the square of the hypotenuse that equals the sum of the squares of the other two sides. For example, if a=3, b=4 and c=5, one of your tests will be 4*4 + 5*5 == 3*3. You need to sort a, b and c before checking the sum of squares, which is a good idea anyway, since the position of the hypotenuse among the parameters is not guaranteed. You could also simplify your code somewhat. Here's one way you could write it:

TOLERANCE = 0.01

def right_triangle?(a, b, c)
  return false if  a == 0 || b == 0 || c == 0
  a, b, c = [a,b,c].sort
  (a**2 + b**2 - c**2).abs < TOLERANCE
end

length = rand(0.01..100.0)
[0.0, length, length].permutation(3).all? { |(a,b,c)| right_triangle?(a,b,c)}
  #=> false

[3,4,5].permutation(3).all? { |(a,b,c)| right_triangle?(a,b,c) }
  #=> true

Since you are dealing with floats, you need to establish some level of tolerance when comparing values for equality. I've used an arbitrary fixed amount (0.01) for demonstration purposes.

Upvotes: 3

Uri Agassi
Uri Agassi

Reputation: 37409

You are returning "false" and "true" instead of false and true, also you check that one+two=three, when you should check one+two==three (an equals check, not an assignment)

def valid_triangle?(a, b, c)
#A Pythagorean triple consists of three positive integers a, b, and c, such that a2 + b2 = c2.
  if a > 0 && b > 0 && c > 0
    one   = a**2
    two   = b**2
    three = c**2
    if one+two == three
      return true
    else
      return false
    end
  else
    return false
  end
end

Upvotes: 2

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