PHP Program to Print uncommon elements from two sorted arrays

Given two sorted arrays of distinct elements, we need to print those elements from both arrays that are not common. The output should be printed in sorted order. 

Examples : 

Input : arr1[] = {10, 20, 30}
        arr2[] = {20, 25, 30, 40, 50}
Output : 10 25 40 50
We do not print 20 and 30 as these
elements are present in both arrays.

Input : arr1[] = {10, 20, 30}
        arr2[] = {40, 50}
Output : 10 20 30 40 50
        

The idea is based on merge process of merge sort. We traverse both arrays and skip common elements.

Steps to find uncommon elements between two sorted arrays:

1. Initialize Pointers:
   • Set three-pointers, i, j, and k, to start at the beginning of arrays arr1, arr2, and the result set respectively.
2. Compare Array Elements:
   • Compare current elements of arr1 and arr2. Print the smaller element if they differ and move the respective pointer.
3. Skip Common Elements:
   • If elements of both arrays are the same, increase both i and j to skip these common elements.
4. Print Remaining Elements:
   • After exiting the loop, print any remaining elements in arr1 or arr2 if one array is longer than the other.
5. Output the Results:
   • Echo each unique element not shared by both arrays, ensuring only uncommon elements are printed.

Below is the implementation of above approach:

<?php
// PHP program to find uncommon 
// elements of two sorted arrays

function printUncommon($arr1, $arr2, 
                       $n1, $n2)
{
    $i = 0;
    $j = 0;
    $k = 0;
    while ($i < $n1 && $j < $n2) 
    {

        // If not common, print smaller
        if ($arr1[$i] < $arr2[$j]) 
        {
            echo $arr1[$i] . " ";
            $i++;
            $k++;
        }
        else if ($arr2[$j] < $arr1[$i]) 
        {
            echo $arr2[$j] . " ";
            $k++;
            $j++;
        }

        // Skip common element
        else 
        {
            $i++;
            $j++;
        }
    }

    // printing remaining elements
    while ($i < $n1) 
    {
        echo $arr1[$i] . " ";
        $i++;
        $k++;
    }
    while ($j < $n2) 
    {
        echo $arr2[$j] . " ";
        $j++;
        $k++;
    }
}

// Driver code
$arr1 = array(10, 20, 30);
$arr2 = array(20, 25, 30, 40, 50);

$n1 = sizeof($arr1) ;
$n2 = sizeof($arr2) ;

printUncommon($arr1, $arr2, $n1, $n2);

// This code is contributed by Anuj_67
?>

10 25 40 50

Complexity Analysis:

• Time Complexity: O(n1 + n2), where n1 and n2 represents the size of the given two arrays.
• Auxiliary Space: O(1), no extra space is required, so it is a constant.

Please refer complete article on Print uncommon elements from two sorted arrays for more details!