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
// Define a function that counts the occurrences of the substring "aa" in the input string
function test($s)
{
    // Initialize a counter for occurrences of "aa"
    $ctr_aa = 0;

    // Iterate through the string, checking for occurrences of "aa"
    for ($i = 0; $i < (strlen($s) - 1); $i++) {
        if (substr($s, $i, 2) == "aa") {
            $ctr_aa++;
        }
    }

    // Return the count of occurrences
    return $ctr_aa;
}

// Test the function with different input strings
echo test("bbaaccaag") . "\n";
echo test("jjkiaaasew") . "\n";
echo test("JSaaakoiaa") . "\n";
?>

Explanation:

• Function Definition:
• The test function takes one parameter, $s, which is a string to check for occurrences of the substring "aa".
• Initialize Counter:
• A variable $ctr_aa is initialized to 0 to keep track of the number of times "aa" appears in the string.
• Loop Through String:
• A for loop iterates through the string from the start to the second-to-last character. The loop runs until strlen($s) - 1 to avoid an out-of-bounds error.
• Check for Substring "aa":
• Inside the loop, substr($s, $i, 2) checks each consecutive pair of characters. If the current two characters are "aa", the counter $ctr_aa is incremented by 1.
• Return Count:
• After the loop completes, the function returns the total count of "aa" occurrences.

Output:

2
2
3

Visual Presentation:

Flowchart:

PHP Code Editor:

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