PHP Challenges: Find a missing number(s) from an array

Last update on June 03 2025 13:00:14 (UTC/GMT +8 hours)

Write a PHP program to find a missing number(s) from an array.

Input : 1,2,3,6,7,8

Explanation :

Sample Solution :

PHP Code :

<?php
// Define a function named missing_number which takes an array $num_list as input
function missing_number($num_list)
{
    // Construct a new array containing the range from the first element to the maximum element in $num_list
    $new_arr = range($num_list[0], max($num_list));                                                    
    // Use array_diff to find the missing elements by comparing $new_arr with $num_list
    return array_diff($new_arr, $num_list);
}

// Test the missing_number function with different input arrays and print the result
print_r(missing_number(array(1,2,3,6,7,8)));
print_r(missing_number(array(10,11,12,14,15,16,17)));
?>

Explanation:

Here is a brief explanation of the above PHP code:

• The code defines a function named 'missing_number' which takes an array '$num_list' as input.
• Inside the function:
• It constructs a new array '$new_arr' using the 'range()' function, which generates an array containing a range of numbers from the first element of '$num_list' to the maximum element in '$num_list'.
• It then uses the 'array_diff()' function to find the elements that are present in `$new_arr` but missing in '$num_list', effectively finding the missing numbers.
• Finally, it returns the array of missing numbers.
• The function is called twice with different input arrays '(1,2,3,6,7,8)' and '(10,11,12,14,15,16,17)'.

Sample Output:

Array                                                                                
(                                                                                    
    [3] => 4                                                                         
    [4] => 5                                                                         
)                                                                                    
Array                                                                                
(                                                                                    
    [3] => 13                                                                        
)             

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