I am writing a c++ code to implement template queue, but when I run my code, I get wrong results, not the expected results, here is the header file and the main code.
queue.h
#include <iostream>
#pragma once
using namespace std;
typedef int Error_code;
#define SUCCESS 0
#define OVERFLOW -1
#define UNDERFLOW -2
template <class T>
class Node{
public:
T item;
Node * next;
Node(){item=0; next=NULL;}
Node(T n){item=n; next=NULL;}
};
template <class T>
class queue
{
protected:
Node *front, *rear;
int count;
public:
queue(){
cout<<"constructor \n";
count = 0;
front = rear = NULL;};
~queue(){Node<T> * p;
while(front != NULL)
{
p = front;
front = front->next;
delete p;
}};
bool isempty(){
//return count == 0;
if(front==NULL)
return true;
else
return false;
};
bool isfull(){return false;};
Error_code serve(){
Error_code outcome = SUCCESS;
Node<T> *p;
if(isempty()){
cout<<"empty queue\n";
outcome=UNDERFLOW;
}
else{
p=front;
front=front->next;
delete p;
count--;
}
return outcome;
} ;
Error_code retrieve(T &item){
Error_code outcome= SUCCESS;
if(isempty())
{ // front node is empty, queue is empty
//return false;
cout<<"empty queue\n";
outcome=UNDERFLOW;
}
return outcome;
};
Error_code append(T item){
Node<T> * n ;
n= new Node; // create node
n->item = item; // set node pointers
n->next = NULL;
if (isempty())
{
rear=front = n;
}
else
{
rear->next = n; // else place at rear
rear = n; // have rear point to new node
}
count++;
return SUCCESS;
};
};
main.cpp
#include "queue.h"
#include <iostream>
using namespace std;
int main()
{
queue<int> q;
queue<char> q2;
int x;
char y;
cout<<"the fisrt queue is :";
q.isempty()?cout<<"empty \n\n":cout<<"not empty \n\n";
cout<<"the second queue is :";
q2.isempty()?cout<<"empty \n\n":cout<<"not empty \n\n";
q.append(2);
q.append(3);
q.append(4);
q2.append('a');
q2.append('b');
q2.append('c');
q.retrieve(x);
cout<<x<<endl;
q.serve();
q.retrieve(x);
cout<<x<<endl;
q.serve();
q.retrieve(x);
cout<<x<<endl;
q.serve();
q2.retrieve(y);
cout<<y<<endl;
q2.serve();
q2.retrieve(y);
cout<<y<<endl;
q2.serve();
q2.retrieve(y);
cout<<y<<endl;
q2.serve();
q.retrieve(x);
q2.retrieve(y);
system("pause");
return 0;
}
I get these results:
constructor
constructor
the first queue is: empty
the second queue is: empty
-858993460
-858993460
-858993460
then it prints some symbols
empty queue
empty queue