PHP Exercises: Read the mass data and find the number of islands

PHP: Exercise-71 with Solution

There are 10 vertical and horizontal squares on a plane. Each square is painted blue and green. Blue represents the sea, and green represents the land. When two green squares are in contact with the top and bottom, or right and left, they are said to be ground. The area created by only one green square is called "island". For example, there are five islands in the figure below.
Write a PHP program to read the mass data and find the number of islands.

Input: A single data set is represented by 10 rows of 10 numbers representing green squares as 1 and blue squares as zeros.

Pictorial Presentation:

Sample Solution:

PHP Code:

<?php
// Function to perform Depth-First Search (DFS)
function dfs(&$field, $s) {
    // Initialize a stack with the starting position
    $stack = array($s);

    // Define movement directions: right, left, down, up
    $dx = array(1, -1, 0, 0);
    $dy = array(0, 0, 1, -1);

    // Continue DFS until the stack is empty
    while (count($stack)) {
        // Pop a node from the stack
        $node = array_pop($stack);

        // Mark the current node as visited
        $field[$node[0]][$node[1]] = '0';

        // Explore neighbors in all four directions
        for ($i = 0; $i < 4; $i++) {
            $nx = $node[1] + $dx[$i];
            $ny = $node[0] + $dy[$i];

            // Check if the neighbor is within the field and is unvisited
            if (!isset($field[$ny][$nx]) || $field[$ny][$nx] === '0') {
                continue;
            }

            // Push the neighbor onto the stack for further exploration
            $stack[] = array($ny, $nx);
        }
    }
}

// Main code block
{ 
    // Initialize a 2D array to represent the field
    $field = array();
    for ($i = 0; $i < 12; $i++) {
        $field[] = str_split(rtrim(fgets(STDIN)));
    }

    // Read an extra line to handle any remaining newline characters
    fscanf(STDIN, '');

    // Initialize a counter for the number of islands
    $c = 0;

    // Iterate through the field
    for ($i = 0; $i < 10; $i++) {
        for ($j = 0; $j < 10; $j++) {
            // If an unvisited '1' is found, perform DFS and increment the island counter
            if ($field[$i][$j] === '1') {
                dfs($field, array($i, $j));
                $c++;
            }
        }
    }

    // Output the number of islands
    echo "Number of islands: \n";
    echo $c . PHP_EOL;
}

?>

Sample Input:
1100000111
1000000111
0000000111
0010001000
0000011100
0000111110
0001111111
1000111110
1100011100
1110001000

Sample Output:

Number of islands: 
5

Flowchart:

PHP Code Editor:

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