Find Second largest element in an array

Given an array of integers, our task is to write a program that efficiently finds the second largest element present in the array.

Example:

Input : arr[] = {12, 35, 1, 10, 34, 1}
Output : The second largest element is 34.

Input : arr[] = {10, 5, 10}
Output : The second largest element is 5.

Input : arr[] = {10, 10, 10}
Output : The second largest does not exist.



A simple solution will be first sort the array in descending order and then return the second element from the sorted array. The time complexity of this solution is O(nlogn).

A Better Solution is to traverse the array twice. In the first traversal find the maximum element. In the second traversal find the greatest element less than the element obtained in first traversal. The time complexity of this solution is O(n).

A more Efficient Solution can be to find the second largest element in a single traversal.
Below is the complete algorithm for doing this:

1) Initialize two variables first and second to INT_MIN as,
   first = second = INT_MIN
2) Start traversing the array,
   a) If the current element in array say arr[i] is greater
      than first. Then update first and second as,
      second = first
      first = arr[i]
   b) If the current element is in between first and second,
      then update second to store the value of current variable as
      second = arr[i]
3) Return the value stored in second.

C

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// C program to find second largest 
// element in an array
  
#include <stdio.h>
#include <limits.h> 
  
/* Function to print the second largest elements */
void print2largest(int arr[], int arr_size)
{
    int i, first, second;
  
    /* There should be atleast two elements */
    if (arr_size < 2)
    {
        printf(" Invalid Input ");
        return;
    }
  
    first = second = INT_MIN;
    for (i = 0; i < arr_size ; i ++)
    {
        /* If current element is greater than first
           then update both first and second */
        if (arr[i] > first)
        {
            second = first;
            first = arr[i];
        }
  
        /* If arr[i] is in between first and 
           second then update second  */
        else if (arr[i] > second && arr[i] != first)
            second = arr[i];
    }
    if (second == INT_MIN)
        printf("There is no second largest element\n");
    else
        printf("The second largest element is %dn", second);
}
  
/* Driver program to test above function */
int main()
{
    int arr[] = {12, 35, 1, 10, 34, 1};
    int n = sizeof(arr)/sizeof(arr[0]);
    print2largest(arr, n);
    return 0;
}

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Java

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// JAVA Code for Find Second largest
// element in an array
class GFG {
      
    /* Function to print the second largest
    elements */
    public static void print2largest(int arr[], 
                                     int arr_size)
    {
        int i, first, second;
       
        /* There should be atleast two elements */
        if (arr_size < 2)
        {
            System.out.print(" Invalid Input ");
            return;
        }
       
        first = second = Integer.MIN_VALUE;
        for (i = 0; i < arr_size ; i++)
        {
            /* If current element is smaller than 
            first then update both first and second */
            if (arr[i] > first)
            {
                second = first;
                first = arr[i];
            }
       
            /* If arr[i] is in between first and 
               second then update second  */
            else if (arr[i] > second && arr[i] != first)
                second = arr[i];
        }
          
        if (second == Integer.MIN_VALUE)
             System.out.print("There is no second largest"+
                                 " element\n");
        else
             System.out.print("The second largest element"+
                                      " is "+ second);
    }
      
    /* Driver program to test above function */
    public static void main(String[] args) 
    {
            int arr[] = {12, 35, 1, 10, 34, 1};
            int n = arr.length;
            print2largest(arr, n);
    }
}
// This code is contributed by Arnav Kr. Mandal.

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Python3

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# Python program to
# find second largest 
# element in an array
  
  
# Function to print the
# second largest elements 
def print2largest(arr,arr_size):
  
    # There should be atleast
        # two elements 
    if (arr_size < 2):
      
        print(" Invalid Input ")
        return
      
  
    first = second = -2147483648
    for i in range(arr_size):
      
        # If current element is
                # smaller than first
        # then update both
                # first and second 
        if (arr[i] > first):
          
            second = first
            first = arr[i]
          
  
        # If arr[i] is in
                # between first and 
        # second then update second 
        elif (arr[i] > second and arr[i] != first):
            second = arr[i]
      
    if (second == -2147483648):
        print("There is no second largest element")
    else:
        print("The second largest element is", second)
  
  
# Driver program to test
# above function 
arr = [12, 35, 1, 10, 34, 1]
n =len(arr)
  
print2largest(arr, n)
  
# This code is contributed
# by Anant Agarwal.

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C#

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// C# Code for Find Second largest
// element in an array
using System;
  
class GFG {
      
    // Function to print the 
    // second largest elements 
    public static void print2largest(int []arr, 
                                    int arr_size)
    {
        int i, first, second;
      
        //There should be atleast two elements
        if (arr_size < 2)
        {
        Console.WriteLine(" Invalid Input ");
            return;
        }
      
        first = second = int.MinValue;
        for (i = 0; i < arr_size ; i++)
        {
            // If current element is smaller than 
            // first then update both first and second
            if (arr[i] > first)
            {
                second = first;
                first = arr[i];
            }
      
            // If arr[i] is in between first  
            // and second then update second 
            else if (arr[i] > second && arr[i] != first)
                second = arr[i];
        }
          
        if (second == int.MinValue)
            Console.Write("There is no second largest"+
                                " element\n");
        else
            Console.Write("The second largest element"+
                                        " is "+ second);
    }
      
    // Driver Code
    public static void Main(String[] args) 
    {
            int []arr = {12, 35, 1, 10, 34, 1};
            int n = arr.Length;
            print2largest(arr, n);
    }
}
  
// This code is contributed by Parashar.

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PHP

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<?php
// PHP program to find second largest 
// element in an array
  
// Function to print the 
// second largest elements
function print2largest($arr, $arr_size)
{
  
    // There should be atleast 
    // two elements 
    if ($arr_size < 2)
    {
        echo(" Invalid Input ");
        return;
    }
  
    $first = $second = PHP_INT_MIN;
    for ($i = 0; $i < $arr_size ; $i++)
    {
          
        // If current element is
        // smaller than first
        // then update both 
        // first and second 
        if ($arr[$i] > $first)
        {
            $second = $first;
            $first = $arr[$i];
        }
  
        // If arr[i] is in 
        // between first and 
        // second then update 
        // second 
        else if ($arr[$i] > $second &&
                 $arr[$i] != $first)
            $second = $arr[$i];
    }
    if ($second == PHP_INT_MIN)
        echo("There is no second largest element\n");
    else
        echo("The second largest element is " . $second . "\n");
}
  
// Driver Code
$arr = array(12, 35, 1, 10, 34, 1);
$n = sizeof($arr);
print2largest($arr, $n);
  
// This code is contributed by Ajit.
?>

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Output:

The second largest element is 34

Time complexity: O(n)
Auxiliary Space : O(1)

Related Article:
Smallest and second smallest element in an array

This article is contributed by Harsh Agarwal. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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