PHP Program to Find the Maximum Element in a Matrix

Given a matrix, the task is to find the maximum element of the matrix (arrays of arrays) in PHP. Finding the maximum element in a matrix is a common task that involves iterating through all the elements of the matrix and keeping track of the largest value found.

Example:

Input: matrix = [
    [1, 2, 3], 
    [4, 5, 6],
    [7, 8, 9]
]

Output: Maximum Element: 9

These are the following approaches:

Approach 1: Using Nested Loops

The basic method to find the maximum element in a matrix is by using nested loops to iterate through each element. PHP_INT_MIN is used to initialize the $max variable to the smallest possible integer value in PHP. The nested foreach loops iterate through each element of the matrix. Inside the inner loop, the $max variable is updated whenever a larger element is found.

Example: This example shows the use of nested loop for finding out the maximum element.

<?php
function findMaxElement($matrix) {

    // Initialize max to the 
    // smallest possible value
    $max = PHP_INT_MIN;
    
    // Iterate through each row 
    // of the matrix
    foreach ($matrix as $row) {
        
        // Iterate through each
        // element of the row
        foreach ($row as $element) {
            
            // Update max if a larger
            // element is found
            if ($element > $max) {
                $max = $element;
            }
        }
    }
    
    return $max;
}

// Driver Code

// Given matrix
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

$max = findMaxElement($matrix);
// Display the maximum element
echo "Maximum Element in the matrix: $max";
?>

Maximum Element in the matrix: 9

Approach 2: Using array_reduce() and max() Functions

Another method to find the maximum element in a matrix is by using the array_reduce() function in combination with the max() function. The array_reduce() is used to iteratively reduce the matrix to a single value, which is the maximum element. The max() function is used twice, once to find the maximum element in each row, and once to compare that value with the current maximum ($carry). PHP_INT_MIN is used as the initial value for $carry to ensure that any element in the matrix will be larger.

Example: This example shows the use of array_reduce() method to find out the max element.

<?php
function findMaxElement($matrix) {

    // Use array_reduce() function to 
    // find the maximum element
    $max = array_reduce($matrix, function ($carry, $row) {
        return max($carry, max($row));
    }, PHP_INT_MIN);
    
    return $max;
}

// Given matrix
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

$max = findMaxElement($matrix);

// Display the maximum element
echo "Maximum Element in the matrix: $max";

?>

Maximum Element in the matrix: 9

Approach 3: Using array_map() and max() Functions

Alternatively, you can use array_map() to apply the max() function to each row of the matrix and then use max() again to find the overall maximum. The array_map('max', $matrix) applies the max() function to each row of the matrix, resulting in an array of maximum values for each row. The max(...) is then used again to find the maximum value in this array of maximum row values.

Example: This example shows the use of array_map() method to find out the max element.

<?php

function findMaxElement($matrix) {

    // Use array_map() function to apply
    // max to each row, then find the
    // max of those values
    $max = max(array_map('max', $matrix));
    
    return $max;
}

// Driver Code

// Given matrix
$matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
];

$max = findMaxElement($matrix);

// Display the maximum element
echo "Maximum Element in the matrix: $max";

?>

Maximum Element in the matrix: 9