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4d47's solution

to Raindrops in the PHP Track

Instructions
Test suite
Solution

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.

Examples

  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

Running the tests

  1. Go to the root of your PHP exercise directory, which is <EXERCISM_WORKSPACE>/php. To find the Exercism workspace run

     % exercism debug | grep Workspace
    
  2. Get PHPUnit if you don't have it already.

     % wget --no-check-certificate https://phar.phpunit.de/phpunit.phar
     % chmod +x phpunit.phar
    
  3. Execute the tests:

     % ./phpunit.phar raindrops/raindrops_test.php
    

Source

A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

raindrops_test.php

<?php

require "raindrops.php";

class RaindropsTest extends PHPUnit\Framework\TestCase
{
    public function test1()
    {
        $this->assertSame("1", raindrops(1));
    }

    public function test3()
    {
        $this->markTestSkipped();
        $this->assertSame("Pling", raindrops(3));
    }

    public function test5()
    {
        $this->markTestSkipped();
        $this->assertSame("Plang", raindrops(5));
    }

    public function test7()
    {
        $this->markTestSkipped();
        $this->assertSame("Plong", raindrops(7));
    }

    public function test6()
    {
        $this->markTestSkipped();
        $this->assertSame("Pling", raindrops(6));
    }

    public function test9()
    {
        $this->markTestSkipped();
        $this->assertSame("Pling", raindrops(9));
    }

    public function test10()
    {
        $this->markTestSkipped();
        $this->assertSame("Plang", raindrops(10));
    }

    public function test14()
    {
        $this->markTestSkipped();
        $this->assertSame("Plong", raindrops(14));
    }

    public function test15()
    {
        $this->markTestSkipped();
        $this->assertSame("PlingPlang", raindrops(15));
    }

    public function test21()
    {
        $this->markTestSkipped();
        $this->assertSame("PlingPlong", raindrops(21));
    }

    public function test25()
    {
        $this->markTestSkipped();
        $this->assertSame("Plang", raindrops(25));
    }

    public function test35()
    {
        $this->markTestSkipped();
        $this->assertSame("PlangPlong", raindrops(35));
    }

    public function test49()
    {
        $this->markTestSkipped();
        $this->assertSame("Plong", raindrops(49));
    }

    public function test52()
    {
        $this->markTestSkipped();
        $this->assertSame("52", raindrops(52));
    }

    public function test105()
    {
        $this->markTestSkipped();
        $this->assertSame("PlingPlangPlong", raindrops(105));
    }

    public function test12121()
    {
        $this->markTestSkipped();
        $this->assertSame("12121", raindrops(12121));
    }
}
<?php

function raindrops($num)
{
    static $factors = [
        3 => 'Pling',
        5 => 'Plang',
        7 => 'Plong',
    ];
    $is_factor = function($fac) use ($num) { return $num % $fac === 0; };
    $words = implode(array_filter($factors, $is_factor, ARRAY_FILTER_USE_KEY));
    return $words ?: "$num";
}

What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

  • What compromises have been made?
  • Are there new concepts here that I could read more about to develop my understanding?