Example: Find Second Smallest and Largest with Two Passes in C

// Find Second Smallest and Largest with Two Passes
#include <stdio.h>
#include <limits.h> // For INT_MAX and INT_MIN

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

    int smallest = INT_MAX, largest = INT_MIN;
    int secondSmallest = INT_MAX, secondLargest = INT_MIN;

    // Pass 1: Find the smallest and largest elements
    for (int i = 0; i < n; i++) {
        if (arr[i] < smallest) {
            smallest = arr[i];
        }
        if (arr[i] > largest) {
            largest = arr[i];
        }
    }

    // Pass 2: Find the second smallest and second largest
    for (int i = 0; i < n; i++) {
        if (arr[i] < secondSmallest && arr[i] != smallest) {
            secondSmallest = arr[i];
        }
        if (arr[i] > secondLargest && arr[i] != largest) {
            secondLargest = arr[i];
        }
    }

    if (secondSmallest != INT_MAX) {
        printf("Second smallest element (two-pass approach): %d\n", secondSmallest);
    } else {
        printf("Second smallest element not found (all elements might be same or array too small).\n");
    }

    if (secondLargest != INT_MIN) {
        printf("Second largest element (two-pass approach): %d\n", secondLargest);
    } else {
        printf("Second largest element not found (all elements might be same or array too small).\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");

    findSecondMinMaxTwoPass(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");
    findSecondMinMaxTwoPass(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");
    findSecondMinMaxTwoPass(arr3, n3);

    return 0;
}