how to use comparitor in priority queu in c++

To use a comparator in a priority queue in C++, you need to define a comparison function or overload the comparison operator (<) for the elements you want to store in the priority queue. Here are the steps to do it:

1. Define a comparison function or overload the comparison operator (<) for the elements you want to store in the priority queue. The comparison function should take two parameters of the same type as the elements and return a boolean value indicating whether the first element should be considered "less than" the second element.

Here's an example of a comparison function: cpp bool compare(int a, int b) { return a > b; // Priority queue with elements in descending order }

And here's an example of overloading the comparison operator: ```cpp struct MyStruct { int value;

   bool operator<(const MyStruct& other) const {
       return value > other.value; // Priority queue with elements in descending order
   }

}; ```

1. Create a priority queue object and specify the comparison function or operator as the second template argument. cpp std::priority_queue<int, std::vector<int>, decltype(&compare)> pq(compare);

or

cpp std::priority_queue<MyStruct> pq;

Note that in the second example, the comparison function or operator is already defined within the MyStruct struct.

1. Add elements to the priority queue using the push() member function. cpp pq.push(10); pq.push(5); pq.push(20);

2. Access the top element of the priority queue using the top() member function. cpp int topElement = pq.top();

Note that the top element will be the element that is considered the highest priority according to the comparison function or operator.

1. Remove the top element from the priority queue using the pop() member function. cpp pq.pop();

After pop(), the next highest priority element will become the new top element.

That's it! You have now used a comparator in a priority queue in C++. The priority queue will automatically maintain the order of the elements based on the comparison function or operator you provided.