Example: Find Second Smallest and Largest by Sorting in C

// Find Second Smallest and Largest by Sorting
#include <stdio.h>
#include <stdlib.h> // For qsort

// Comparison function for qsort (ascending order)
int compare(const void *a, const void *b) {
    return (*(int*)a - *(int*)b);
}

void findSecondMinMaxSorted(int arr[], int n) {
    if (n < 2) {
        printf("Array must have at least two elements.\n");
        return;
    }

    // Sort the array in ascending order
    qsort(arr, n, sizeof(int), compare);

    int secondSmallest = -1;
    int secondLargest = -1;

    // Find second smallest (skipping duplicates of the smallest)
    int i;
    for (i = 1; i < n; i++) {
        if (arr[i] > arr[0]) { // arr[0] is the smallest
            secondSmallest = arr[i];
            break;
        }
    }

    // Find second largest (skipping duplicates of the largest)
    for (i = n - 2; i >= 0; i--) {
        if (arr[i] < arr[n - 1]) { // arr[n-1] is the largest
            secondLargest = arr[i];
            break;
        }
    }

    if (secondSmallest != -1) {
        printf("Second smallest element (sorted approach): %d\n", secondSmallest);
    } else {
        printf("Second smallest element not found (all elements might be same).\n");
    }

    if (secondLargest != -1) {
        printf("Second largest element (sorted approach): %d\n", secondLargest);
    } else {
        printf("Second largest element not found (all elements might be same).\n");
    }
}

int main() {
    int arr[] = {12, 35, 1, 10, 34, 1};
    int n = sizeof(arr) / sizeof(arr[0]);

    printf("Original array: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");

    findSecondMinMaxSorted(arr, n);

    int arr2[] = {5, 5, 5, 5};
    int n2 = sizeof(arr2) / sizeof(arr2[0]);
    printf("\nOriginal array 2: ");
    for (int i = 0; i < n2; i++) {
        printf("%d ", arr2[i]);
    }
    printf("\n");
    findSecondMinMaxSorted(arr2, n2);

    int arr3[] = {7};
    int n3 = sizeof(arr3) / sizeof(arr3[0]);
    printf("\nOriginal array 3: ");
    for (int i = 0; i < n3; i++) {
        printf("%d ", arr3[i]);
    }
    printf("\n");
    findSecondMinMaxSorted(arr3, n3);

    return 0;
}