QueueUsingArray1.cpp

#include <iostream>
using namespace std;
#define n 20
class queue{
    int * arr;
    int front;
    int back;

    public:
    queue(){
        arr=new int[n];
        front=-1, back=-1;
    }
    void push(int x){
        if(back==n-1){
            cout<<"Queue overflow"<<endl;
        }
        back++;
        arr[back]=x;

        if(front==-1){
            front++;
        }
    }

    void pop(){
        if(front==-1 || front>back){
            cout<<"No elements in queue"<<endl;
            return;
        }
        front++;
    }

    int peek(){
        if(front==-1 || front>back){
            cout<<"No elements in queue"<<endl;
            return -1;
        }
        return arr[front];

    }

    bool empty(){
        if(front==-1 || front>back){
            return true;
        }
        return false;

    }
};

int main()
{
    queue q;
    q.push(1);
    q.push(2);
    q.push(3);
    q.push(4);

    cout<<q.peek()<<endl;
    q.pop();
    cout<<q.peek()<<endl;
    q.pop();
    cout<<q.peek()<<endl;
    q.pop();
    cout<<q.peek()<<endl;
    q.pop();
    cout<<q.empty()<<endl;
    return 0;
}