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import java.util.LinkedList; import java.util.Queue; import java.util.Stack; import java.util.Scanner; public class App { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter the number of integers: "); int numIntegers = scanner.nextInt(); scanner.nextLine(); // Consume the newline character System.out.print("Enter the value of K: "); int k = scanner.nextInt(); scanner.nextLine(); // Consume the newline character Queue<Integer> queue = new LinkedList<>(); System.out.println("Enter " + numIntegers + " integers:"); for (int i = 0; i < numIntegers; i++) { int num = scanner.nextInt(); queue.add(num); } System.out.println("Original queue: " + queue); reverseKElements(queue, k); System.out.println("After reversing first " + k + " elements: " + queue); scanner.close(); // Close the scanner } public static void reverseKElements(Queue<Integer> queue, int k) { if (k <= 0 || k > queue.size()) { return; // Invalid input } Stack<Integer> stack = new Stack<>(); // Push the first K elements of the queue into a stack for (int i = 0; i < k; i++) { stack.push(queue.poll()); } // Pop elements from the stack and enqueue them back into the queue while (!stack.isEmpty()) { queue.add(stack.pop()); } // Dequeue and enqueue the remaining elements to maintain order for (int i = 0; i < queue.size() - k; i++) { queue.add(queue.poll()); } } }
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