Priority Queue of pointers C++

Question

class Edge; 

class Node
{
        public:
        Node(): distance(numeric_limits<double>::infinity()), visited(false) {}
        Node(string a_id): distance(numeric_limits<double>::infinity()), visited(false), id(a_id) {}
        bool operator==(const Node& p) {return p.id == id; }


        string id;
        double distance;
        bool visited;
        string previous;
        vector<Edge*> edges; 
};

class Edge
{
    public:
        Edge(double weight, string id)
        {
            this->weight = weight;
            dest = new Node(id);
        }
        double weight;
        Node * dest;

};
class Comparator {
public:
    bool operator()(const Node* a, const Node* b)
    {
        return (a->distance > b->distance);
    }
};

These are my classes. I created a priority queue from vector of node pointers:

priority_queue<Node*, vector<Node*>, Comparator > queue;

But after some operations I get segmentation fault.

queue.push(nodes[0]);
queue.pop();
queue.push(nodes[1]);
queue.push(nodes[4]);


queue.pop();
queue.push(nodes[3]);
queue.push(nodes[5]);

queue.pop();
queue.push(nodes[6]);
queue.push(nodes[7]);
nodes[6]->distance=1;
queue.pop();

At the last line

     queue.pop();

I get an segmentation fault and I don't get it why it happens. Thanks in advance.

Answer 1

I added

#include <limits>
#include <queue>
#include <string>
#include <vector>
using namespace std;

to the top of your file and used the following main():

int main(int argc, char* argv[])
{
    priority_queue<Node*, vector<Node*>, Comparator > queue;
    vector<Node> vnode(10);
    vector<Node*> nodes(10);
    for (int i = 0; i < 10; ++i)
    {
        vnode[i].distance = i;
        nodes[i] = &vnode[i];
    }

    queue.push(nodes[0]);
    queue.pop();
    queue.push(nodes[1]);
    queue.push(nodes[4]);


    queue.pop();
    queue.push(nodes[3]);
    queue.push(nodes[5]);

    queue.pop();
    queue.push(nodes[6]);
    queue.push(nodes[7]);
    nodes[6]->distance=1;
    queue.pop();
}

It compiles and runs without a segfault, so I'm guessing your nodes aren't all initialized? Also, the line nodes[6]->distance=1; didn't cause node 6 to pop() next; it still popped node 4 there, but then reordered the rest of the queue with node 6 first, then 5, then 7.