Find the Second Largest Element in an Array in PHP

We will be given with an integer array, i.e. $array1 or $ array2, and the task is to find the second largest element in the array. There are multiple ways to approach and solve this problem however using sorting is the most common and concise approach as we use the rsort() function for further operations. These problems are useful in data analysis and for algorithm design.

These types of problem in PHP can be solved using the following three approaches:

Using Sorting method

Here, we are going to Sort the array ($arr) in descending order and then return the element at index 1, which will be the second largest element.

Example: This example shows the use of sorting method to find the second largest element.

<?php
function findSecondLargest($arr)
{
    $size = count($arr);

    if ($size < 2) {
        return "Array should have at least two elements.";
    }
    rsort($arr);
    return $arr[1];
}

$numbers = [10, 5, 8, 12, 6, 3, 9];
$secondLargest = findSecondLargest($numbers);

echo "Original array: " . implode(", ", $numbers) . "\n";
echo "Second largest element: " . $secondLargest;

Original array: 10, 5, 8, 12, 6, 3, 9
Second largest element: 10

Using Two Variables Approach

We are going to define a function namely findSecondLargest() that takes an array $arr as input. We initialize two variables, $largest and $secondLargest, with the first element of the array. Then, we will iterate over each element $num in the array using a foreach loop. Inside the loop, we compare $num with $largest and when the loop ends, $secondLargest will hold the second largest element in the array, which is then returned by the function.

Example: This example shows the use of Two Variables to find the second largest element.

<?php
function findSecondLargest($arr)
{
    $largest = $arr[0];
    $secondLargest = $arr[0];

    foreach ($arr as $num) {
        if ($num > $largest) {
            $secondLargest = $largest;
            $largest = $num;
        } elseif ($num > $secondLargest && $num != $largest) {
            $secondLargest = $num;
        }
    }
    return $secondLargest;
}
$numbers = [10, 5, 8, 20, 12, 20, 15];
$secondLargest = findSecondLargest($numbers);
echo "The second largest element is: " . $secondLargest;
?>

The second largest element is: 15

Remove Largest Element Approach

We are going to use that function which first finds the largest element in the array. It then removes it from the array using PHP array_diff(). In the remaining array, the function finds the largest element again, which is 18. Then, the second largest element in the given array is printed as the output.

Example: This example shows the use of removal of largest element to find the second largest element.

<?php
function findSecondLargest($arr)
{
    $n = count($arr);
    $largest = $arr[0];
    for ($i = 1; $i < $n; $i++) {
        if ($arr[$i] > $largest) {
            $largest = $arr[$i];
        }
    }
    $arr = array_diff($arr, [$largest]);
    $secondLargest = $arr[0];
    foreach ($arr as $num) {
        if ($num > $secondLargest) {
            $secondLargest = $num;
        }
    }
    return $secondLargest;
}
$numbers = [10, 5, 8, 20, 15, 3, 12, 9, 7, 2, 18, 6, 11, 4, 14];
$secondLargest = findSecondLargest($numbers);
echo "The second largest element is: " . $secondLargest;
?>

The second largest element is: 18

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