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Reverse first k elements of queue

Here given code implementation process.

/*
    C++ program 
    Reverse first k elements of queue
*/
#include <iostream>
#include <stack>
#include <queue>

using namespace std;
// Handles the request to reverse initial k elements
void reverseElement(queue <int> &q, int k)
{
    if (q.size() < k || q.empty())
    {
        return;
    }
    // Create an stack
    stack < int > s;
    int n = q.size();
    int counter = 0;
    // Add initial k queue element into stack
    while (counter < k)
    {
        s.push(q.front());
        // Remove a front node of queue
        q.pop();
        counter++;
    }
    // Add inserting stack element back to queue
    while (!s.empty())
    {
        q.push(s.top());
        s.pop();
    }
    counter = 0;
    // Reverse inital  n - k queue element
    while (counter < n - k)
    {
        q.push(q.front());
        q.pop();
        counter++;
    }
}
// Handles the request of printing queue elements
void printQueue(queue <int> q)
{
    // Display Queue element
    while (!q.empty())
    {
        cout <<"  "<< q.front() ;
        q.pop();
    }
}
int main(int argc, char const *argv[])
{
    queue < int > q;
    // Add element into queue
    q.push(1);
    q.push(2);
    q.push(3);
    q.push(4);
    q.push(5);
    q.push(6);
    q.push(7);
    cout << "\n Before Reverse "<< endl;
    printQueue(q);
    int k = 3;
    // Reverse the initially k element
    reverseElement(q, k);
    cout << "\n After Reverse initial " << k << " Element" <<endl;
    printQueue(q);
    return 0;
}

Output

 Before Reverse
  1  2  3  4  5  6  7
 After Reverse initial 3 Element
  3  2  1  4  5  6  7
/*
    Java Program 
    Reverse first k elements of queue
*/
import java.util.Queue;
import java.util.Stack;
import java.util.LinkedList;
public class Reverse
{
	// Handles the request to reverse initial k elements
	public void reverseElement(Queue <Integer> q, int k)
	{
		if (q.size() < k || q.isEmpty())
		{
			return;
		}
		// Create an stack
		Stack <Integer> s = new Stack <Integer> ();
		// Get number of element in queue
		int n = q.size();
		int counter = 0;
		// Add initial k queue element into stack
		while (counter < k)
		{
			s.push(q.peek());
			// Remove a front node of queue
			q.remove();
			counter++;
		}
		// Add inserting stack element back to queue
		while (!s.empty())
		{
			q.add(s.peek());
			s.pop();
		}
		counter = 0;
		// Reverse inital  n - k queue element
		while (counter < n - k)
		{
			q.add(q.peek());
			q.remove();
			counter++;
		}
	}
	// Handles the request of printing queue elements
	public void printQueue(Queue <Integer> q)
	{
		for (Integer item: q)
		{
			System.out.print("  " + item);
		}
	}
	public static void main(String[] args)
	{
		Reverse task = new Reverse();
		Queue <Integer> q = new LinkedList<Integer> ();
		q.add(1);
		q.add(2);
		q.add(3);
		q.add(4);
		q.add(5);
		q.add(6);
		q.add(7);
		System.out.println("\n Before Reverse ");
		task.printQueue(q);
		int k = 3;
		task.reverseElement(q, k);
		System.out.println("\n After Reverse intial " + k);
		task.printQueue(q);
	}
}

Output

 Before Reverse
  1  2  3  4  5  6  7
 After Reverse intial 3
  3  2  1  4  5  6  7
/*
    C# Program 
    Reverse first k elements of queue
*/
// Include namespace system
using System;
using System.Collections;
public class Reverse
{
	public static Queue q = new Queue();
	// Handles the request to reverse initial k elements
	public void reverseElement(int k)
	{
		if (q.Count < k || q.Count == 0)
		{
			return;
		}
		// Create an stack
		Stack s = new Stack();
		// Get number of element in queue
		int n = q.Count;
		int counter = 0;
		// Add initial k queue element into stack
		while (counter < k)
		{
			s.Push(q.Peek());
			// Remove a front node of queue
			q.Dequeue();
			counter++;
		}
		// Add inserting stack element back to queue
		while (s.Count > 0)
		{
			q.Enqueue(s.Peek());
			s.Pop();
		}
		counter = 0;
		// Reverse inital  n - k queue element
		while (counter < n - k)
		{
			q.Enqueue(q.Peek());
			q.Dequeue();
			counter++;
		}
	}
	// Handles the request of printing queue elements
	public void printQueue()
	{
		foreach(var item in q)
		{
			Console.Write("  {0}", item);
		}
	}
	public static void Main(String[] args)
	{
		Reverse task = new Reverse();
		q.Enqueue(1);
		q.Enqueue(2);
		q.Enqueue(3);
		q.Enqueue(4);
		q.Enqueue(5);
		q.Enqueue(6);
		q.Enqueue(7);
		Console.WriteLine("\n Before Reverse ");
		task.printQueue();
		int k = 3;
		task.reverseElement(k);
		Console.WriteLine("\n After Reverse intial " + k);
		task.printQueue();
	}
}

Output

 Before Reverse
  1  2  3  4  5  6  7
 After Reverse intial 3
  3  2  1  4  5  6  7
# Python 3 program
# Reverse first k elements of queue

from queue import Queue 

class Reverse :
    #  Handles the request to reverse initial k elements
    def reverseElement(self, q, k) :
        if (q.qsize() < k or q.empty()) :
            return
        
        #  Create an list
        s = []
        #  Get number of element in queue
        n = q.qsize()
        counter = 0
        #  Add initial k queue element into list
        while (counter < k) :
            s.append(q.get())
            #  Remove a front node of queue
            counter += 1
        
        #  Add inserting list element back to queue
        while (len(s)>0) :
            q.put(s.pop())
      
        
        counter = 0

        #  Reverse inital  n - k queue element
        while (counter < n - k) :
            q.put(q.get())
            
            counter += 1
        
    
    #  Handles the request of printing queue elements
    def printQueue(self, q) :
        n = q.qsize()
        for x in range(0,n):
            print("",q.queue[x],end="")
        

def main() :
    task = Reverse() 
    q = Queue()
    q.put(1)
    q.put(2)
    q.put(3)
    q.put(4)
    q.put(5)
    q.put(6)
    q.put(7)
    print("\n Before Reverse ")
    task.printQueue(q)
    k = 3
    task.reverseElement(q, k)
    print("\n After Reverse intial", k,"element")
    task.printQueue(q)

if __name__ == "__main__": main()

Output

 Before Reverse
 1 2 3 4 5 6 7
 After Reverse intial 3 element
 3 2 1 4 5 6 7
#  Ruby program
#  Reverse first k elements of queue

class Reverse 
    #  Handles the request to reverse initial k elements
    def reverseElement(q, k) 
        if (q.length < k || q.length == 0 || k < 0) 
            return 
        end
        #  Create an array
        s = []
        #  Get number of element in q
        n = q.length
        counter = 0
        #  Add initial k (q) element into s
        while (counter < k) 
            s << (q.at(0))
            #  Remove a front node of q
            q.delete_at(0)
            counter += 1
        end
       
        #  Add inserting s element back to q
        while (s.length > 0) 
            q.insert(0,s.at(0))
            s.delete_at(0)
        end
    end

    #  Handles the request of printing queue elements
    def printQueue(q)
        i = 0 
        while (i < q.length) 
            print("  ", q.at(i))
            i = i + 1
        end
    end

end

def main() 
    task = Reverse.new() 
    q = []
    q << 1
    q << 2
    q << 3
    q << 4
    q << 5
    q << 6
    q << 7
    print("\n Before Reverse \n")
    task.printQueue(q)
    k = 3
    task.reverseElement(q, k)
    print("\n After Reverse intial ", k,"\n")
    task.printQueue(q)
end

main()

Output

 Before Reverse 
  1  2  3  4  5  6  7
 After Reverse intial 3
  3  2  1  4  5  6  7
Last updated on by Kalkicode




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