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());
}
}
}