priority queue with min heap
This is frequently used in Competitive Programming.
We first multiply all elements with (-1). Then we create a max heap (max heap is the default for priority queue).
When we access the data and want to print it we simply multiply those elements with (-1) again.Difference between Priority Queue and Heap
This website provides a really clear explanation. http://pages.cs.wisc.edu/~vernon/cs367/notes/11.PRIORITY-Q.html
In short, a priority queue can be implemented using many of the data structures that we've already studied (an array, a linked list, or a binary search tree). However, those data structures do not provide the most efficient operations. To make all of the operations very efficient, we'll use a new data structure called a heap.priority queue min heap
#include <bits/stdc++.h>
using namespace std;
// User defined class, Point
class Point
{
int x;
int y;
public:
Point(int _x, int _y)
{
x = _x;
y = _y;
}
int getX() const { return x; }
int getY() const { return y; }
};
// To compare two points
class myComparator
{
public:
int operator() (const Point& p1, const Point& p2)
{
return p1.getX() > p2.getX();
}
};
// Driver code
int main ()
{
// Creates a Min heap of points (order by x coordinate)
priority_queue <Point, vector<Point>, myComparator > pq;
// Insert points into the min heap
pq.push(Point(10, 2));
pq.push(Point(2, 1));
pq.push(Point(1, 5));
// One by one extract items from min heap
while (pq.empty() == false)
{
Point p = pq.top();
cout << "(" << p.getX() << ", " << p.getY() << ")";
cout << endl;
pq.pop();
}
return 0;
}Copyright © 2021 Codeinu
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