abcd

#include<bits/stdc++.h>
using namespace std;
vector<int> q;

 void push(int d){
   q.insert(q.end(),d);
 }

 void pop(){
 q.erase(q.begin());
 }

 int front(){
 return *q.begin();
 }

 int main(){
    push(1);
    push(2);
    push(3);
    push(4);
    pop();
    cout<<front()<<endl;
     for(int i=0;i<q.size();i++) cout<<q[i]<<" ";
  }

//////////////
tree.h()
{
Private:
Typename Template<T> current;
queue<Node> traversal;
void add(root);
...
}
 
 
constructor()
{
if(root_)
{
add(root_)
++*this
}
else
current = NULL;
}
void add(root)
{
if(root_->data < 0) //mine wanted the negative numbers
traversal.push(root);
if(root->left)
add(root->left)
if(root->right)
add(root->right)
}
 
operator++{
if(traversal.size() == 0)
    current = NULL;
else {
current = traversal.top();
traversal.pop();
}
return *this;
}
operator *
{
return current->data;
 
 
}