Sorting a queue - C/C++ - c++

Question

I have created a queue that in each node there are three information. I want to create a member function in class that sorts the queue when called. I wish to have the queue sorted by time? (it is an int and a member of q_node). This queue needs to be sorted in such a way that the lowest value of 'time' is in the front and it is sorted in increasing order.
My code for my Queue is found below:
typedef struct Qnode{
int time;
char name[10];
char value;
struct Qnode *q_next;
struct Qnode *q_prev;
} q_node;
class Queue{
private:
q_node *q_rear;
q_node *q_front;
int number;
public:
Queue();
void enqueue(int time, char *s, char value);
q_node *q_top(){
return q_front;
}
void dequeue();
void display();
void queueSort();
bool isEmpty();
};
Queue::Queue(){
q_rear = NULL;
q_front = NULL;
number = 0;
}
bool Queue::isEmpty(){
if (q_front == NULL)
return true;
else
return false;
}
void Queue::enqueue(int t, char *n, char v){
q_node *q_temp = new q_node;
q_temp->time = t;
strcpy(q_temp->name , n);
q_temp->value = v;
q_temp->q_next = NULL;
if(q_front == NULL){
q_front = q_temp;
}
else{
q_rear->q_next = q_temp;
}
q_rear = q_temp;
number++;
}
void Queue::dequeue(){
q_node *q_temp = new q_node;
q_temp = q_front;
q_front = q_front -> q_next;
number--;
delete q_temp;
}
void Queue::display(){
q_node *p = new q_node;
p = q_front;
while(p!=NULL){
cout<< "\ntime: " << p->time;
cout<< "\nname: " << p->name;
cout<< "\nvalue: " << p->value;
cout << endl;
p = p->q_next;
}
}
void Queue::queueSort(){
//Code for sorting
}

Answer 1

One way is to dump the queue into an array or vector by using dequeue, use std::sort and then rebuild the queue from scratch by using your enqueue function. This is clean and avoids messing up with pointers. This is also optimal because running time is dominated by time it takes to sort.
Something like:
v = vector of nodes
while(Q.isEmpty() == false)
{ v.push_back(*Q.top());
Q.dequeue();
}
sort(v.begin(), v.end(), cmp);
for(int i = 0; i < v.size(); i++)
{ Q.enqueue(v[i].time, v[i].name, v[i].value);
}
Where cmp compares nodes by time.

Answer 2

Find the node with the smallest time field, remove it from the list and make it the head of a new list. Then continue to do this, appending the nodes to the new list, in a loop while the original list is not empty. When the original list is empty, take the new (sorted) list and make it the new queue.
It might not be especially efficient, but should work fine.