PHP Searching and Sorting Algorithm: Selection sort

PHP Searching and Sorting Algorithm: Exercise-4 with Solution

Write a PHP program to sort a list of elements using Selection sort.

The selection sort improves on the bubble sort by making only one exchange for every pass through the list.

Visual Presentation : Selection Sort

Sample Solution :

PHP Code :

<?php
// Function to perform selection sort on an array
function selection_sort($data)
{
    // Loop through the array
    for ($i = 0; $i < count($data) - 1; $i++) {
        $min = $i;
        // Find the minimum element in the remaining unsorted array
        for ($j = $i + 1; $j < count($data); $j++) {
            if ($data[$j] < $data[$min]) {
                $min = $j;
            }
        }
        // Swap the minimum element with the first unsorted element
        $data = swap_positions($data, $i, $min);
    }
    return $data;
}

// Function to swap two elements in an array
function swap_positions($data1, $left, $right)
{
    // Backup the value of the element at the right position
    $backup_old_data_right_value = $data1[$right];
    // Swap the elements at the left and right positions
    $data1[$right] = $data1[$left];
    $data1[$left] = $backup_old_data_right_value;
    return $data1;
}

// Input array to be sorted
$my_array = array(3, 0, 2, 5, -1, 4, 1);

// Print the original array
echo "Original Array :\n";
echo implode(', ', $my_array);
echo "\nSorted Array :\n";

// Perform selection sort on the array and print the sorted array
echo implode(', ', selection_sort($my_array)) . PHP_EOL;
?>

Output:

Original Array :                                                    
3, 0, 2, 5, -1, 4, 1                                                
Sorted Array :                                                      
-1, 0, 1, 2, 3, 4, 5

Explanation:

In the exercise above,

• Function selection_sort($data):
• This function takes an array '$data' as input and sorts it using the selection sort algorithm.
• It iterates through the array and selects the minimum element in each iteration, swapping it for the element at the current position.
• Function swap_positions($data1, $left, $right):
• This function takes an array '$data1' and two indices '$left' and '$right' as input.
• It swaps the elements at positions '$left' and '$right' in the array '$data1'.
• Main code:
• An input array '$my_array' is defined with unsorted numbers.
• The original array is printed.
• The "selection_sort()" function is called to sort the array.
• The sorted array is printed.

• Selection Sorting Algorithm:
• The selection sort algorithm works by dividing the input array into two subarrays: sorted and unsorted.
• In each iteration, it finds the minimum element from the unsorted subarray and places it at the beginning of the sorted subarray.
• This process continues until the entire array is sorted.
• Code execution:
• The "selection_sort()" function iterates through the array.
• In each iteration, it finds the minimum element in the unsorted part of the array using nested loops.
• It swaps the minimum element with the current element at the beginning of the unsorted part.
• After iterations, the array is sorted, and the sorted array is returned.

Flowchart :

PHP Code Editor:

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