C program to find second largest number in array

Write a C program to find largest and second largest element in an array. How to find second largest element in array in C programming language. Logic to find second largest element in array in C program.

Example

Input

Input array elements: -7 2 3 8 6 6 75 38 3 2

Output

Second largest = 38

Required knowledge

Basic Input Output, If else, For loop, Array

Logic to find second largest element

Second largest element in array

Step by step descriptive logic to find second largest element in array.

  1. Input size and elements in array, store it in some variable say size and arr.
  2. Declare two variables max1 and max2 to store first and second largest elements. Store minimum integer value in both i.e. max1 = max2 = INT_MIN.
  3. Iterate though all array elements, run a loop from 0 to size - 1. Loop structure should look like for(i=0; i<size; i++).
  4. Inside loop, check if current array element is greater than max1, then make largest element as second largest and current array element as largest. Say, max2 = max1 and max1 = arr[i].
  5. Else if the current array element is greater than max2 but less than max1 then make current array element as second largest i.e. max2 = arr[i].

Program to find second largest element in array

/**
 * C program to find second largest number in an array
 */

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

#define MAX_SIZE 1000     // Maximum array size 

int main()
{
    int arr[MAX_SIZE], size, i;
    int max1, max2;

    /* Input size of the array */
    printf("Enter size of the array (1-1000): ");
    scanf("%d", &size);

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

    max1 = max2 = INT_MIN;


    /*
     * Check for first largest and second
     */
    for(i=0; i<size; i++)
    {
        if(arr[i] > max1)
        {
            /*
             * If current element of the array is first largest
             * then make current max as second max
             * and then max as current array element
             */
            max2 = max1;
            max1 = arr[i];
        }
        else if(arr[i] > max2 && arr[i] < max1)
        {
            /*
             * If current array element is less than first largest
             * but is greater than second largest then make it
             * second largest
             */
            max2 = arr[i];
        }
    }

    printf("First largest = %d\n", max1);
    printf("Second largest = %d", max2);

    return 0;
}

Output

Enter size of the array (1-1000): 10
Enter elements in the array: -7 2 3 8 6 6 75 38 3 2
First largest = 75
Second largest = 38

Happy coding 😉

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