PHP exercises with arrays

array_exercises.php

<?php

/**
 * --------------------------------------------------------------
 * Programming exercises arrays and loops
 * --------------------------------------------------------------
 * source: https://gist.github.com/Kaapiii/b78116341de9fcd16a62792945c11537
 *
 * Task: solve all tasks by using one of the four loop types. The same loop type can be used for all functions.
 *
 * Execute file: "php -f array_exercises.php"
 */


// Test data for exercises
$testA = [4, 6, 0, 3, 7, 10, 4, 5, 6, 9, 3, 8, 9, 0, 3, 5, 3, 4, 9, 4];
$testB = [3, 14, 15, 13, 5, 3, 14, 8, 12, 11, 13, 14, 15, 2, 3, 15, 8, 1, 12, 0, 6, 9, 11, 0, 14, 5, 2, 2, 15, 13];
$testC = [2,3,4,5,6,7,8];

/**
 * ---------------------------------------
 * Examples functions with different loops
 * ---------------------------------------
 */
function echoElements(array $input)
{
    $max = count($input);
    // --------------------
    // Common loops
    // --------------------
    // Desc: These loops will terminate and won't loop forever.

    // for loop
    for ($i = 0; $i < $max; $i++) {
        echo $input[$i];
    }
    echo PHP_EOL;

    // foreach loop
    foreach ($input as $item) {
        echo $item;
    }
    echo PHP_EOL;

    // --------------------
    // Less common loops
    // --------------------
    // Desc: These loops can loop forever, if the condition and increment are set wrong.

    // while loop
    $i = 0;
    while ($i < $max) {
        echo $input[$i];
        $i++; // increment i, otherwise it will loop forever
    }
    echo PHP_EOL;

    // do while
    $j = 0;
    do {
        echo $input[$j];
        $j++; // increment i, otherwise it will loop forever
    } while ($j < $max);
    echo PHP_EOL;
}

// Output/Echo with loops
echoElements($testB);

// Output/echo with created helper function
println($testB);


/**
 * -------------------------------
 * Exercises / Tasks
 * -------------------------------
 */

/**
 * Find the lowest number in array
 *
 * @param array $arrayA
 * @return int
 */
function findLowest(array $arrayA): int
{
    // @Todo Code here and update return type
    return 0;
}
//$result1 = findLowest($testA);
//$result2 = findLowest($testB);
//println($result1);
//println($result2);
// shorter method
// println(findLowest($testA));


/**
 * Find the highest number in array
 *
 * @param array $arrayA
 * @return int
 */
function findHighest(array $arrayA): int
{
    // @Todo Code here and update return type
    return 0;
}
//println(findHighest($testA));
//println(findHighest($testB));

/**
 * Find combine two arrays and return the combined result array
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return array
 */
function combineArrays(array $arrayA, array $arrayB): array
{
    // @Todo Code here and update return type
    return [];
}
//println(combineArrays($testA, $testB));


/**
 * Find combine two arrays and count elements number in array
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return int
 */
function combineArraysAndCountElements(array $arrayA, array $arrayB): int
{
    // @Todo Code here and update return type
    return 0;
}
//println(combineArraysAndCountElements($testA, $testB));


/**
 * Find combine two arrays and sum all values
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return int
 */
function combineArraysAndSum(array $arrayA, array $arrayB): int
{
    // @Todo Code here and update return type
    return 0;
}
//println(combineArraysAndSum($testA, $testB));


/**
 * Find all even numbers
 *
 * @param array $arrayA
 * @return int
 */
function findAllEvenNumbers(array $arrayA): int
{
    // @Todo Code here and update return type
    return 0;
}
//println(findAllEvenNumbers($testA));
//println(findAllEvenNumbers($testB));


/**
 * Find all even numbers
 *
 * @param array $arrayA
 * @return int
 */
function findAllOddNumbers(array $arrayA): int
{
    // @Todo Code here and update return type
    return 0;
}
//println(findAllOddNumbers($testA));
//println(findAllOddNumbers($testB));


//-------------------------------------
// Find the errors and correct them
//-------------------------------------

/**
 * This function has a small error. Find it and fix it.
 * Runtime Message: "PHP Notice:  Undefined offset: 30 in ...."
 *
 * Hint: use the debugger
 */
function findTheErrorRemoveTheNotice(array $input)
{
    $max = count($input);
    // while loop
    $i = 0;
    while ($i < $max) {
        echo $input[$i];
        $i++; // increment i, otherwise it will loop forever
    }
    echo PHP_EOL;

    // do while
    do {
        echo $input[$i];
        $i++; // increment i, otherwise it will loop forever
    } while ($i < $max);
    echo PHP_EOL;
}
findTheErrorRemoveTheNotice($testB);

//-------------------------------------
// Advanced - Sorting
//-------------------------------------

/**
 * Find combine two arrays and order values ascending
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return array
 */
function combineArraysAndSortAsc(array $arrayA, array $arrayB): array
{
    // @Todo Code here and update return type
    return [];
}
//println(combineArraysAndSortAsc($testA, $testB));


/**
 * Find combine two arrays and order values descending
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return array
 */
function combineArraysAndSortDesc(array $arrayA, array $arrayB): array
{
    // @Todo Code here and update return type
    return [];
}
//println(combineArraysAndSortDesc($testA, $testB));

/**
 * Add a new number at beginning of the array
 *
 * @param array $arrayA
 * @param int $newNumber
 * @return array
 */
function addAsFirstElement(array $arrayA, int $newNumber): array
{
    // @Todo Code here and update return type
    return [];  // should return [1,2,3,4,5,6,7,8]
}
//println(addAsFirstElement($testA, 1));

/**
 * Add a new number at the  of the array
 *
 * @param array $arrayA
 * @param array $arrayB
 * @return array
 */
function addAsLastElement(array $arrayA, int $newNumber): array
{
    // @Todo Code here and update return type
    return [];  // should return [2,3,4,5,6,7,8,9]
}
//println(addAsLastElement($testA, 9));

/**
 * Add a new number at the given position and reorder the other numbers
 *
 * @param array $arrayA
 * @param int $newNumber
 * @param int $position
 * @return array
 */
function addElementAtPosition(array $arrayA, int $newNumber, int $position): array
{
    // @Todo Code here and update return type
    return [];  // should return [2,3,4,100,5,6,7,8,9]  -> note that array index start with index "0".
}
//println(addElementAtPosition($testA, 100, 3));

/**
 * Replace a element/value at a given position
 *
 * @param array $arrayA
 * @param int $newNumber
 * @param int $position
 * @return array
 */
function replaceElementAtPosition(array $arrayA, int $newNumber, int $position): array
{
    // @Todo Code here and update return type
    return [];  // should return [4, 6, 0, 3, 7, 100, 4, 5, 6, 9, 3, 8, 9, 0, 3, 5, 3, 4, 9, 4]
}
//println(replaceElementAtPosition($testA, 100, 6));


/**
 * Replace all occurrences of a value with a new value
 *
 * @param array $arrayA
 * @param int $searchValue
 * @param int $replaceValue
 * @return array
 */
function replaceAllWith(array $arrayA, int $searchValue, int $replaceValue): array
{
    // @Todo Code here and update return type
    return [];  // should return [100, 6, 0, 3, 7, 10, 100, 5, 6, 9, 3, 8, 9, 0, 3, 5, 3, 100, 9, 100];
}
//println(replaceAllWith($testA, 4, 100));


//-------------------------------------
// Helper methods
//-------------------------------------
function println($input): void
{
    if (is_array($input)) {
        echo implode(', ', $input) . PHP_EOL;
        return;
    }
    echo $input . PHP_EOL;
}