Matt Lake
Code Challenge, searching through arrays

Code Challenge, searching through arrays

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Matthew Lake
·

3 min read

This is the first in a series of code challenges that we will solve using PHP, let's jump straight in.

The Problem

This problem was asked by Google.

Given a list of numbers and a number k, return whether any two numbers from the list add up to k. For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.
- dailycodingproblem.com

Testing

Before starting the challenge I put together a few simple tests. We could use a library such as PHPUnit or PestPHP, but as we are only testing one simple method we will create the test case ourself.

// Test Data
$testData = [
    ['list' => [10, 15, 3, 7], 'key' => 17, 'expected' => true],
    ['list' => [2, 4, 6, 8, 10], 'key' => 16, 'expected'=> true],
    ['list' => [1, 3, 5, 7, 9, 11], 'key' => 24, 'expected' => false],
    ['list' => [0, 99, 158, 2000], 'key' => 865, 'expected' => false],
    ['list' => [23, 48, 76, 4, 25, 18, 32, 22, 67, 12], 'key' => 37, 'expected' => true],
    ['list' => [12], 'key' =>12, 'expected' => false],
    ['list' => [6,3,8], 'key' => 12, 'expected'=> false],
];

// Test Method
function testMethod(array $testData)
{
  foreach($testData as $test) {
    if($test['expected'] != checkSum($test['list'], $test['key'])) {
      echo "Test " . implode(', ', $test['list']) . ":  RESULT: *** FAIL ***".PHP_EOL;
      continue;
    }

    echo "Test " . implode(', ', $test['list']) . ":  RESULT: ----PASS----".PHP_EOL;
  }
}

My Solution

First we will look at the code and then describe my thinking.

/* The Alogorithm */
function checkSum(array $list, int $k)
{
  foreach($list as $key => $value) {
    if(in_array($k - $value, $list) && array_search($k-$value, $list) != $key){
        return true;
    }
  }

  return false;
}

// Run the tests
testMethod($testData);

The solution I have chosen to take is a simple one.

  • We iterate through the given list which gives us the $value variable. We then know that we are looking for the result of $k - $value in our array.
  • We check that $value is in the array using the inbuilt in_array() method.
  • We then do another check to make sure that we are not using the same value from the array twice using the inbuilt array_search() method.

When we run our script in the console we should get

Test 2, 4, 6, 8, 10:  RESULT: ----PASS----
Test 1, 3, 5, 7, 9, 11:  RESULT: ----PASS----
Test 0, 99, 158, 2000:  RESULT: ----PASS----
Test 23, 48, 76, 4, 25, 18, 32, 22, 67, 12:  RESULT: ----PASS----
Test 12:  RESULT: ----PASS----
Test 6, 3, 8:  RESULT: ----PASS----

Conclusion

There we have it, fairly straight forward using inbuilt array methods. How would you have done it?

PHPcoding challengearray methods