PHP Exercises: Count a substring of length 2 appears in a given string and also as the last 2 characters of the string

PHP Basic Algorithm: Exercise-31 with Solution

Write a PHP program to count a substring of length 2 appears in a given string and also as the last 2 characters of the string. Do not count the end substring.

Sample Solution:

PHP Code :

<?php
// Define a function that counts the occurrences of the last two characters in substrings of the input string
function test($s)
{
    // Extract the last two characters of the input string
    $last_two_char = substr($s, strlen($s)-2, 2);

    // Initialize a counter variable
    $ctr = 0;

    // Iterate through the string (excluding the last two characters)
    for ($i = 0; $i < strlen($s)-2; $i++) {
        // Check if the current substring matches the last two characters
        if (substr($s, $i, 2) == $last_two_char) {
            // Increment the counter
            $ctr = $ctr + 1;
        }
    }

    // Return the final count
    return $ctr;
}

// Test the function with different input strings
echo test("abcdsab")."\n";
echo test("abcdabab")."\n";
echo test("abcabdabab")."\n";
echo test("abcabd")."\n";
?>

Explanation:

• Function Definition:
• The test function takes a string $s and counts occurrences of its last two characters within the rest of the string.
• Extract Last Two Characters:
• The last two characters of $s are extracted and stored in $last_two_char using substr($s, strlen($s) - 2, 2).
• Initialize Counter:
• A counter variable $ctr is initialized to zero to keep track of occurrences.
• Iterate Through String:
• A for loop iterates over $s from the beginning to the second-last character (i.e., strlen($s) - 2).
• For each position $i, it checks if the substring from $i of length 2 matches $last_two_char.
• Increment Counter:
• If a match is found, $ctr is incremented by one.
• Return Final Count:
• After the loop, the function returns $ctr, which is the count of occurrences.

Output:

1
2
3
0

Visual Presentation:

Flowchart:

PHP Code Editor:

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