data-structures-and-algorithms/linklistusingqueue.cpp at main · Open-code-source/data-structures-and-algorithms · GitHub

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#include<iostream>
using namespace std;

class node{
    public:

    int data;
    node *next;
    public:
    node(int val){
        data=val;
        next=NULL;
    }

};

class queue{

    node *front;
    node *back;
    public:

        queue(){
        front=NULL;
        back=NULL;
    }

    void push(int x){
        node *n=new node(x);
        if(front==NULL){
            back=n;
            front=n;
            return;
        }
        back->next=n;
        back=n;
    }

    void pop(){
        if(front==NULL){
            cout<<"queue is empty"<<endl;
        }

        node *temp=front;
        front=front->next;
        delete temp;
    }

    int peek(){
         if(front==NULL){
            cout<<"queue is empty"<<endl;
            return -1;
        }
        return front->data;
    }

    bool empty(){
        if(front==NULL){
            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;

}