l61.cpp

#include<iostream>
using namespace std;
class kQueue{
    public:
    int n;
    int k;
    int *front;
    int *rear;
    int *arr;
    int freeSpot;
    int *next;
    public:
    kQueue(int n, int k){
        this->n = n;
        this->k = k;
        front = new int[k];
        rear = new int[k];
        for(int i = 0; i<k; i++){
            front[i] = -1;
            rear[i] = -1;
        }
        next = new int[n];
        for(int i = 0; i<n; i++){
            next[i] = i+1;
        }
        arr = new int[n];
        freeSpot = 0;
    }
    void enqueue(int data, int qn){
        //overflow
        if(freeSpot == -1){
            cout<<"No empty space is present"<<endl;
            return;
        }
        //find first free index
        int index = freeSpot;
        //update freeSpot
        freeSpot = next[index];
        //check whether first element
        if(front[qn-1]== -1){
            front[qn-1] = index;
        }
        else{
            //link new element to the prev element
            next[rear[qn-1]] = index;
        }
        // update next 
        next[index] = -1;
        // update rear 
        rear[qn-1] = index;
        //push element
        arr[index] = data;
    }
    int dequeue(int qn){
        //underflow
         if(front[qn-1] == -1){
            cout<<"Queue underflow"<<endl;
            return -1;
         }
         //find index to top
         int index = front[qn-1];
         //front ko aage badhao khatam ho jate hai.
         front[qn-1] = next[index];
         //freeSlots ko manage karo
         next[index] = freeSpot;
         freeSpot = index;
         return arr[index];
    }
};
int main(){
    kQueue q(10,3);
    q.enqueue(10, 1);
    q.enqueue(15,1);
    q.enqueue(20, 2);
    q.enqueue(25, 1);
    cout<<"Dequeued element is "<<q.dequeue(1)<<endl;
    cout<<"Dequeued element is "<<q.dequeue(1)<<endl;
    cout<<"Dequeued element is "<<q.dequeue(1)<<endl;
    cout<<"Dequeued element is "<<q.dequeue(1)<<endl;
    cout<<"Dequeued element is "<<q.dequeue(1)<<endl;

    return 0;
}