Example: Find Second Largest Element (Single-Pass Scan) in C

// Find Second Largest Element (Single-Pass Scan)
#include <stdio.h>
#include <limits.h> // For INT_MIN

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

    if (n < 2) {
        printf("Array must have at least two elements.\n");
        return 0;
    }

    // Initialize largest and secondLargest
    // Ensure largest is initially greater or equal to secondLargest (or they are distinct sentinels)
    int largest = INT_MIN, secondLargest = INT_MIN;

    // Handle initial two elements if possible to set a baseline
    // Or initialize with first relevant values, careful with duplicates
    // Robust initialization: iterate from start and update
    for (int i = 0; i < n; i++) {
        if (arr[i] > largest) {
            secondLargest = largest; // The old largest becomes the new second largest
            largest = arr[i];        // Update largest
        } else if (arr[i] > secondLargest && arr[i] < largest) {
            secondLargest = arr[i]; // Update second largest only if it's distinct and smaller than largest
        }
    }

    if (secondLargest == INT_MIN) {
        printf("No second distinct largest element found.\n");
    } else {
        printf("The second largest element is: %d\n", secondLargest);
    }

    return 0;
}