CODEWITHSUNDEEP
c++
chris edwards
chris edwards

Reputation: 1432

C++ trying to use priority queue with a custom class, compiler is throwing errors why trying to populate the queue

I am trying to create an A* search for a 2d array of integers in c++ (im very new to c++ but i have done one in Java loads of times) the problem is when i trying to push items into the queue it throws a compilation error due a type conflict.

My Node.h is defined as:

class Node{

private:

    int xCoord;
    int yCoord;
    int value;
    Node* parent;

public:

    Node();
    Node(int x, int y, int value);
    void setParent(Node* parent);
    int getX();
    int getY();
    int getValue();
    Node* getParent();
    bool operator()(Node& node1, Node& node2);

};

struct NodeCompare {

    bool operator()(Node& node1, Node& node2) const
    {
        int node1value = node1.getValue();
        int node2value = node2.getValue();
        return node1value < node2value;
    }
};

Node.cpp:

#include <stdlib.h>

#include "Node.h"

Node::Node(){

    this->xCoord = -1;
    this->yCoord = -1;
    this->value = -1;
    this->parent = NULL;

}

Node::Node(int _x, int _y, int _value){

    this->xCoord = _x;
    this->yCoord = _y;
    this->value = _value;
    this->parent = NULL;

}

void Node::setParent(Node* par){

    this->parent = par;

}

int Node::getX(){

    return xCoord;

}

int Node::getY(){

    return yCoord;

}

int Node::getValue(){

    return value;

}

Node* Node::getParent(){

    return parent;
}

bool Node::operator()(Node& node1, Node& node2) {

return node1.value > node2.value;

}

and my main:

#include <iostream>
#include <ostream>
#include <vector>
#include <queue>

#include "Node.h"

int main(){

    using namespace std;

    priority_queue<Node, vector<Node>, NodeCompare> openList;

    Node* node = new Node(1,2,19);

    openList.push(node);

    cout << "node is: x " << node->getX() << " y " << node->getY() << " value "
            << node->getValue() << endl;



    return 0;

}

The compiler says:

error: no matching function for call to ‘std::priority_queue<Node, std::vector<Node>, NodeCompare>::push(Node*&)’

which is to do with the type of Node i am trying to push onto the list (so i believe) i have tried changing my code to the following:

Node node = new Node(1,2,19);

which gives the error:

error: conversion from ‘Node*’ to non-scalar type ‘Node’ requested

and i have tried passing in all the variations i know:

openList.push(&node);

and

openList.push(*node);

But they also throw compilation errors.

Can someone explain what i am doing wrong?

Cheers, Chris.

Upvotes: 0

Views: 642

Answers (2)

Alex
Alex

Reputation: 699

You're trying to add a node pointer to a list of node objects. What I would recommend is openList.push(*node);.

Upvotes: 1

A.E. Drew
A.E. Drew

Reputation: 2137

new returns a pointer to an object while your priority queue is declared to hold actual objects. You can change main like so to just deal with a Node object rather than a pointer to a Node on the heap:

int main(){

    using namespace std;

    priority_queue<Node, vector<Node>, NodeCompare> openList;

    Node node = Node(1,2,19);

    openList.push(node);

    cout << "node is: x " << node.getX() << " y " << node.getY() << " value "
            << node.getValue() << endl;



    return 0;

}

Upvotes: 1

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