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PHP Exercises: Count the string "aa" in a given string and assume "aaa" contains two "aa"

PHP Basic Algorithm: Exercise-27 with Solution

Write a PHP program to count the string "aa" in a given string and assume "aaa" contains two "aa".

Sample Solution:

PHP Code :

<?php
function test($s)
{
   $ctr_aa = 0;
   for ($i = 0; $i < (strlen($s) - 1); $i++)
            {
                if (substr($s, $i, 2) == "aa")
                {
                    $ctr_aa++;
                }
            }
            return $ctr_aa;
 }


echo test("bbaaccaag")."\n";
echo test("jjkiaaasew")."\n";
echo test("JSaaakoiaa")."\n";

Sample Output:

2
2
3

Pictorial Presentation:

PHP Basic Algorithm Exercises: Count the string 'aa' in a given string and assume 'aaa' contains two 'aa'.

Flowchart:

Flowchart: Count the string 'aa' in a given string and assume 'aaa' contains two 'aa'.

PHP Code Editor:

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Previous: Write a PHP program to create a new string which is n (non-negative integer) copies of the the first 3 characters of a given string. If the length of the given string is less than 3 then return n copies of the string.
Next: Write a PHP program to check if the first appearance of "a" in a given string is immediately followed by another "a".

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.



PHP: Tips of the Day

How to Sort Multi-dimensional Array by Value?

Try a usort, If you are still on PHP 5.2 or earlier, you'll have to define a sorting function first:

Example:

function sortByOrder($a, $b) {
    return $a['order'] - $b['order'];
}

usort($myArray, 'sortByOrder');

Starting in PHP 5.3, you can use an anonymous function:

usort($myArray, function($a, $b) {
    return $a['order'] - $b['order'];
});

And finally with PHP 7 you can use the spaceship operator:

usort($myArray, function($a, $b) {
    return $a['order'] <=> $b['order'];
});

To extend this to multi-dimensional sorting, reference the second/third sorting elements if the first is zero - best explained below. You can also use this for sorting on sub-elements.

usort($myArray, function($a, $b) {
    $retval = $a['order'] <=> $b['order'];
    if ($retval == 0) {
        $retval = $a['suborder'] <=> $b['suborder'];
        if ($retval == 0) {
            $retval = $a['details']['subsuborder'] <=> $b['details']['subsuborder'];
        }
    }
    return $retval;
});

If you need to retain key associations, use uasort() - see comparison of array sorting functions in the manual

Ref : https://bit.ly/3i77vCC