CPP/LinkedListQueue.cpp at main · FreeDSA/CPP · GitHub

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#include<bits/stdc++.h>

using namespace std;

class node{
    public:
    int data;
    node* next;
    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;
        // delete n;
    }

    void pop(){
        if(front==NULL){
            cout<<"Queue is Empty"<<endl;
            return;
        }
        node* todel=front;
        front=front->next;
        delete todel;
    }

    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);
    q.push(5);

    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.peek()<<endl;
    q.pop();

    cout<<q.empty()<<endl;

    return 0;
}