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Posted on Oct 7, 2019

Daily Challenge #84 - Third Angle of a Triangle

#challenge

You are given two angles of a triangle in degrees.

Write a function to return the third angle. Only positive integers will be tested.

Sample Tests:

thirdAngle(30, 60) thirdAngle(60, 60) thirdAngle(43, 78) thirdAngle(10, 20)

This challenge comes from user5651159. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Want to propose a challenge idea for a future post? Email yo+challenge@dev.to with your suggestions!

Top comments (16)

Kona Arctic • Oct 7 '19 • Edited

ANSI C

#include <math.h>

double third_angle ( double first_angle , double second_angle ) {
    first_angle = fmod( first_angle , 360.0 );  // Get absolute
    second_angle = fmod( second_angle , 360.0 );

    if ( first_angle + second_angle >= 180 )
        return 0.0;  // That's not a triangle! OwO

    return ( 180 - first_angle - second_angle );
}

int main ( int argc , char ** argv ) {
    if ( 
        ( int ) third_angle( 30 , 60 ) == 90 &&
        ( int ) third_angle( 60 , 60 ) == 60 &&
        ( int ) third_angle( 43 , 78 ) == 59 &&
        ( int ) third_angle( 10 , 20 ) == 150 )
            return 0;  // It works!

    return 101;  // Or not
}

Run with ~$ gcc -lm <file_name> && ./a.out

Iano Njuguna • Dec 13 '22

Kept it simple

#include <stdio.h>

int other_angle(int a, int b) 
{
    return(180 - a - b);
}

K.V.Harish • Oct 7 '19 • Edited

My solution in js

const thirdAngle = (angle1, angle2) => (angle1 && angle2 && (angle3 = 180 - (angle1 + angle2)) > 0) ? angle3 : 'Invalid - Sum of all angles of a triangle should be 180 degrees';

Josh • Oct 7 '19

What happens if I enter thirdAngle(0,0)?

K.V.Harish • Oct 7 '19 • Edited

Good catch. Edited. But the challenge is to deal with positive integers so didn't take 0 into account as it is neither positive nor negative integer.

Josh • Oct 7 '19

True enough. But why code purely for specs when coding for the edge and error cases takes just a few more minutes?

willsmart • Oct 7 '19

Keeping it simple in bash

function thirdAngle {
  echo $((180 - $1 - $2))
}

Running through the examples on the cmd:

> thirdAngle 30 60
90

> thirdAngle 60 60
60

> thirdAngle 43 78
59

> thirdAngle 10 20
150

willsmart • Oct 7 '19

BTW the challenge on Kata only tests for valid triangles,

function otherAngle(a, b) {
  return 180-(a+b);
}

was sufficient in JS

Josh • Oct 7 '19

This oughta do it for Elixir.

defmodule Triangle do
  def third_angle(a, b) when is_integer(a + b) # will not qualify if either isn't an integer
                         and a + b < 180 
                         and a > 0
                         and b > 0 do
    180 - a - b
  end
end

Peter • Oct 7 '19

In Go!

func thirdAngle(a, b int) (int, error) {
    if (a + b) >= 180 {
        return 0, errors.New("Input angles sum is greater than or equal to 180 degress, this cannot be a triangle")
    }
    if a == 0 || b == 0 {
        return 0, errors.New("Input angle cannot be zero, cannot be a triangle")
    }
    angle := 360 - a - b // sum of angles must be 360 degress
    return angle, nil
}

Go Playground

Amin • Oct 8 '19

Elm

import List exposing (all, sum)
import Maybe exposing (andThen, map)


isAngle : Int -> Bool
isAngle angle =
    angle > 0 && angle < 180


maybeAngles : List Int -> Maybe (List Int)
maybeAngles angles =
    if all isAngle angles && sum angles < 180 then
        Just angles

    else
        Nothing


third : Int -> Int -> Maybe Int
third first second =
    maybeAngles [ first, second ]
        |> map (sum >> (-) 180)

Test it online

Here.

Michael Baas • Oct 9 '19 • Edited

Solution in APL

(using Dyalog APL)

thirdAngle←{r←180-+/⍵ ⋄ (r<0)∨0∊⍵: 'This is not a triangle!' ⋄ r}

Tests:

      thirdAngle 30 60
90
      thirdAngle 60 60
60
      thirdAngle 43 78
59
      thirdAngle 10 20
150

Try it online!

DeLiXx • Oct 8 '19 • Edited

function thirdAngle(a,b) {
    return 180-a-b;
}

lormayna • Oct 7 '19 • Edited

Josh • Oct 7 '19 • Edited

What happens if I enter thirdAngle(0,0)?

lormayna • Oct 8 '19

you are right, I just wrote it very fast and I did not think about this case.
TDD will help a lot in these situations.

View full discussion (16 comments)