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:

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

Sample Solution: -

PHP Code:


    $field = array();
    for ($i = 0; $i < 12; $i++) {
        $field[] = str_split(rtrim(fgets(STDIN)));
    fscanf(STDIN, '');
    $c = 0;
    for ($i = 0; $i < 10; $i++) {
        for ($j = 0; $j < 10; $j++) {
            if ($field[$i][$j] === '1') {
                dfs($field, array($i, $j));
    echo "Number of islands: \n";
    echo $c . PHP_EOL;
function dfs(&$field, $s) {
    $stack = array($s);
    $dx = array(1, -1, 0, 0);
    $dy = array(0, 0, 1, -1);
    while (count($stack)) {
        $node = array_pop($stack);
        $field[$node[0]][$node[1]] = '0';
        for ($i = 0; $i < 4; $i++) {
            $nx = $node[1] + $dx[$i];
            $ny = $node[0] + $dy[$i];
            if (!isset($field[$ny][$nx]) || $field[$ny][$nx] === '0') {
            $stack[] = array($ny, $nx);

Sample Input:

Sample Output:

Number of islands: 


Flowchart: Read the mass data and find the number of islands.

PHP Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: Write a PHP program to find the customer number that has traded for the second consecutive for the second consecutive month from last month and the number of transactions.
Next: Write a PHP program to restore the original string by entering the compressed string with this rule.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.

PHP: Tips of the Day

Why shouldn't I use mysql_* functions in PHP?

The MySQL extension:

  • Is not under active development
  • Is officially deprecated as of PHP 5.5 (released June 2013).
  • Has been removed entirely as of PHP 7.0 (released December 2015)
  • This means that as of 31 Dec 2018 it does not exist in any supported version of PHP. If you are using a version of PHP which supports it, you are using a version which doesn't get security problems fixed.
  • Lacks an OO interface
  • Doesn't support:
    • Non-blocking, asynchronous queries
    • Prepared statements or parameterized queries
    • Stored procedures
    • Multiple Statements
    • Transactions
    • The "new" password authentication method (on by default in MySQL 5.6; required in 5.7)
    • Any of the new functionality in MySQL 5.1 or later

Since it is deprecated, using it makes your code less future proof.

Lack of support for prepared statements is particularly important as they provide a clearer, less error-prone method of escaping and quoting external data than manually escaping it with a separate function call.

Ref : https://bit.ly/2BIIsF0