Example: FindSecondSmallest_TwoPass in Java

// FindSecondSmallest_TwoPass
public class Main {
    public static int findSecondSmallestTwoPass(int[] arr) {
        if (arr == null || arr.length < 2) {
            System.out.println("Array must contain at least two elements.");
            return -1;
        }

        // Step 1: Find the smallest element
        int smallest = Integer.MAX_VALUE;
        for (int num : arr) {
            if (num < smallest) {
                smallest = num;
            }
        }

        // Step 2: Find the second smallest element
        // Initialize secondSmallest to MAX_VALUE to ensure any valid number will be smaller
        int secondSmallest = Integer.MAX_VALUE;
        for (int num : arr) {
            // If the current number is smaller than secondSmallest
            // AND it's not equal to the smallest element found in Step 1
            if (num < secondSmallest && num != smallest) {
                secondSmallest = num;
            }
        }

        // If secondSmallest is still Integer.MAX_VALUE, it means either
        // all elements are the same as 'smallest', or there was no distinct second smallest.
        if (secondSmallest == Integer.MAX_VALUE) {
            System.out.println("No distinct second smallest element found.");
            return -1;
        }

        return secondSmallest;
    }

    public static void main(String[] args) {
        int[] arr1 = {12, 5, 2, 10, 8, 2, 1};
        System.out.println("Original array: " + java.util.Arrays.toString(arr1));
        System.out.println("Second smallest element (Two Pass): " + findSecondSmallestTwoPass(arr1)); // Output: 5

        int[] arr2 = {7, 7, 3, 3, 5};
        System.out.println("Original array: " + java.util.Arrays.toString(arr2));
        System.out.println("Second smallest element (Two Pass): " + findSecondSmallestTwoPass(arr2)); // Output: 5

        int[] arr3 = {10, 10, 10, 10};
        System.out.println("Original array: " + java.util.Arrays.toString(arr3));
        System.out.println("Second smallest element (Two Pass): " + findSecondSmallestTwoPass(arr3)); // Output: -1

        int[] arr4 = {5};
        System.out.println("Original array: " + java.util.Arrays.toString(arr4));
        System.out.println("Second smallest element (Two Pass): " + findSecondSmallestTwoPass(arr4)); // Output: -1
    }
}