当我尝试使用带有参数的priority_queue作为指向结构的指针时，为什么会弹出错误

Question

## Priority Queue throws an error with pointers. When I try to use structure pointers as parameter for priority queue and use comparator function the code gives an error, but priority seems to work fine with objects. ##

 #include<bits/stdc++.h>
 using namespace std;
 struct data
 {
    int cost;
    int node;
    int k;
    data(int a,int b,int c):cost(a),node(b),k(c){};
 };

 struct cmp
 {
    bool operate(data *p1,data *p2)
    {
    return p1->cost<p2->cost;
    }
 };

 int main ()
 {

    priority_queue<data*,vector<data*>,cmp> pq; 
    pq.push(new data(0,2,3)); //This line throws an error stating (   required from here) and there is nothing written before required.

 }

Answer 1

There are 3 things wrong with your code:

1) There is a std::data that exists in C++ 17, yet you have a struct data with the addition of using namespace std; before the declaration of struct data . This could cause a naming clash.

2) The function call operator is operator() , not operate .

3) You're using the dreaded #include <bits/stdc++.h> , which not only is non-standard, causes all sorts of issues pertaining to item 1) above.

Here is your code that addresses all of these issues above:

 #include <vector>
 #include <queue>

 struct data
 {
    int cost;
    int node;
    int k;
    data(int a,int b,int c):cost(a),node(b),k(c){};
 };

 struct cmp
 {
    bool operator()(data *p1,data *p2)
    {
        return p1->cost < p2->cost;
    }
 };

 int main ()
 {
    std::priority_queue<data*, std::vector<data*>,cmp> pq; 
    pq.push(new data(0,2,3)); 
 }

Live Example