C Program to Find the Second Largest Element in an Array

Introduction

Finding the second largest element in an array involves determining the largest element first and then finding the next largest element. This guide will show you how to write a C program to identify the second largest element in an array provided by the user.

Problem Statement

Create a C program that:

• Takes the size of the array as input from the user.
• Takes the elements of the array as input.
• Finds the second largest element in the array.
• Displays the second largest element.

Example:

• Input: Array size = 6, Elements = [12, 35, 1, 10, 34, 1]
• Output: Second largest element = 34

Solution Steps

1. Include the Standard Input-Output Library: Use #include <stdio.h> to include the standard input-output library, which is necessary for using printf and scanf functions.
2. Write the Main Function: Define the main function, which is the entry point of every C program.
3. Declare Variables: Declare variables to store the array size, the array elements, and the largest and second largest elements.
4. Input the Array Size: Use scanf to take input from the user for the size of the array.
5. Input the Array Elements: Use a loop to take input from the user for the elements of the array.
6. Find the Largest and Second Largest Elements: Use a loop to find the largest and second largest elements in the array.
7. Display the Second Largest Element: Use printf to display the second largest element.

C Program

#include <stdio.h>
#include <limits.h>  // For INT_MIN

/**
 * C Program to Find the Second Largest Element in an Array
 * Author: https://www.javaguides.net/
 */
int main() {
    // Step 1: Declare variables to hold the array size, elements, and largest/second largest elements
    int n, i;
    int largest, second_largest;

    // Step 2: Prompt the user to enter the size of the array
    printf("Enter the number of elements in the array: ");
    scanf("%d", &n);

    // Step 3: Declare an array to hold the elements
    int arr[n];

    // Step 4: Input the array elements
    printf("Enter %d elements:\n", n);
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    // Step 5: Initialize largest and second_largest
    largest = second_largest = INT_MIN;

    // Step 6: Find the largest and second largest elements
    for (i = 0; i < n; i++) {
        if (arr[i] > largest) {
            second_largest = largest;
            largest = arr[i];
        } else if (arr[i] > second_largest && arr[i] != largest) {
            second_largest = arr[i];
        }
    }

    // Step 7: Check if second_largest exists
    if (second_largest == INT_MIN) {
        printf("There is no second largest element in the array.\n");
    } else {
        printf("The second largest element is %d\n", second_largest);
    }

    return 0;  // Step 8: Return 0 to indicate successful execution
}

Explanation

Step 1: Declare Variables

• The variable n is declared to store the size of the array. largest and second_largest are used to store the largest and second largest elements in the array, respectively. The variable i is used as a loop counter.

Step 2: Input the Array Size

• The program prompts the user to enter the size of the array using printf. The scanf function then reads the input and stores it in the variable n.

Step 3: Declare the Array

• The program declares an array arr of size n to hold the elements provided by the user.

Step 4: Input the Array Elements

• The program uses a for loop to take input for each element of the array. The loop iterates from 0 to n-1, reading the elements using scanf.

Step 5: Initialize largest and second_largest

• Both largest and second_largest are initialized to INT_MIN (a constant defined in limits.h representing the minimum integer value). This ensures that any element in the array will be larger than the initial values.

Step 6: Find the Largest and Second Largest Elements

• The program uses a for loop to iterate through the array:
  • If an element is greater than largest, second_largest is updated to the current value of largest, and largest is updated to the current element.
  • If an element is greater than second_largest but not equal to largest, it becomes the new second_largest.

Step 7: Check if second_largest Exists

• After the loop, the program checks if second_largest is still INT_MIN. If it is, this means no second largest element was found (e.g., all elements were the same), and an appropriate message is displayed.

Step 8: Display the Second Largest Element

• If a second largest element is found, it is displayed using the printf function.

Step 9: Return 0

• The return 0; statement indicates that the program executed successfully.

Output Example

Example 1:

Enter the number of elements in the array: 6
Enter 6 elements:
12
35
1
10
34
1
The second largest element is 34

Example 2 (All elements are the same):

Enter the number of elements in the array: 4
Enter 4 elements:
7
7
7
7
There is no second largest element in the array.

Example 3 (Negative numbers):

Enter the number of elements in the array: 5
Enter 5 elements:
-3
-1
-7
-4
-2
The second largest element is -2

Conclusion

This C program demonstrates how to find the second largest element in an array. It covers basic concepts such as arrays, loops, conditional statements, and edge case handling, making it a useful example for beginners learning C programming.