PHP Searching and Sorting Algorithm: Selection sort

Last update on December 20 2024 10:28:01 (UTC/GMT +8 hours)

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

PHP sharp selection short

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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