PHP Exercises: Compare two given strings and return the number of the positions where they contain the same length 2 substring

PHP Basic Algorithm: Exercise-35 with Solution

Write a PHP program to compare two given strings and return the number of the positions where they contain the same length 2 substring.

Sample Solution:

PHP Code :

<?php
// Define a function that counts the number of common two-character substrings between two strings
function test($s1, $s2)
{
    // Initialize a counter variable
    $ctr = 0;

    // Iterate through substrings of the first string
    for ($i = 0; $i < strlen($s1)-1; $i++)
    {
        // Extract a two-character substring from the first string
        $firstString = substr($s1, $i, 2);

        // Iterate through substrings of the second string
        for ($j = 0; $j < strlen($s2)-1; $j++)
        {
            // Extract a two-character substring from the second string
            $secondString = substr($s2, $j, 2);

            // Check if the two substrings are equal, and increment the counter if they are
            if ($firstString == $secondString) 
                $ctr++;
        }
    }

    // Return the final count of common two-character substrings
    return $ctr;
}

// Test the function with different pairs of strings
echo (test("abcdefgh", "abijsklm"))."\n";
echo (test("abcde", "osuefrcd"))."\n";
echo (test("pqrstuvwx", "pqkdiewx"))."\n";
?>

Explanation:

• Function Definition:
• The test function takes two strings, $s1 and $s2, and counts the number of common two-character substrings between them.
• Counter Initialization:
• A variable $ctr is initialized to keep track of the count of matching two-character substrings.
• Iterate through $s1:
• The outer for loop iterates through each possible two-character substring in $s1.
• For each index i, substr($s1, $i, 2) extracts a two-character substring from $s1, stored in $firstString.
• Iterate through $s2:
• The inner for loop iterates through each possible two-character substring in $s2.
• For each index j, substr($s2, $j, 2) extracts a two-character substring from $s2, stored in $secondString.
• Compare Substrings:
• If $firstString is equal to $secondString, the counter $ctr is incremented.
• Return Result:
• After all comparisons, the function returns $ctr, representing the number of common two-character substrings between $s1 and $s2.

Output:

1
1
2

Flowchart:

PHP Code Editor:

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