Question

C++ Question

Can I get an example of a max heap that has an insert function, delete function and a print function?

Please use namespace std and iostream and whatever else is needed I guess.

Answer 1

`Hey,

Note: Brother in case of any queries, just comment in box I would be very happy to assist all your queries

#include <iostream>
#include<vector>
using namespace std;

// Data structure for Max Heap
struct PriorityQueue
{
private:
   // vector to store heap elements
   vector<int> A;

   // return parent of A[i]
   // don't call this function if it is already a root node
   int PARENT(int i)
   {
       return (i - 1) / 2;
   }

   // return left child of A[i]
   int LEFT(int i)
   {
       return (2 * i + 1);
   }

   // return right child of A[i]
   int RIGHT(int i)
   {
       return (2 * i + 2);
   }

   // Recursive Heapify-down algorithm
   // the node at index i and its two direct children
   // violates the heap property
   void heapify_down(int i)
   {
       // get left and right child of node at index i
       int left = LEFT(i);
       int right = RIGHT(i);

       int largest = i;

       // compare A[i] with its left and right child
       // and find largest value
       if (left < size() && A[left] > A[i])
           largest = left;

       if (right < size() && A[right] > A[largest])
           largest = right;

       // swap with child having greater value and
       // call heapify-down on the child
       if (largest != i) {
           swap(A[i], A[largest]);
           heapify_down(largest);
       }
   }

   // Recursive Heapify-up algorithm
   void heapify_up(int i)
   {
       // check if node at index i and its parent violates
       // the heap property
       if (i && A[PARENT(i)] < A[i])
       {
           // swap the two if heap property is violated
           swap(A[i], A[PARENT(i)]);

           // call Heapify-up on the parent
           heapify_up(PARENT(i));
       }
   }

public:
   // return size of the heap
   unsigned int size()
   {
       return A.size();
   }

   // function to check if heap is empty or not
   bool empty()
   {
       return size() == 0;
   }

   // insert key into the heap
   void insert(int key)
   {
       // insert the new element to the end of the vector
       A.push_back(key);

       // get element index and call heapify-up procedure
       int index = size() - 1;
       heapify_up(index);
   }

   // function to remove element with highest priority (present at root)
   void deletes()
   {

           // if heap has no elements, throw an exception
           if (size() == 0)
               {
               cout<<"Can't delete empty heap\n";
return;
               }

           // replace the root of the heap with the last element
           // of the vector
           A[0] = A.back();
           A.pop_back();

           // call heapify-down on root node
           heapify_down(0);

   }

   // function to return element with highest priority (present at root)
   int top()
   {

           // if heap has no elements, throw an exception
           if (size() == 0)
               {
               cout<<"Can't return empty heap\n";
return -1;
               }

           // else return the top (first) element
           return A.at(0);   // or return A[0];

       // catch and print the exception

   }
};

int main()
{
   PriorityQueue pq;

   // Note - Priority is decided by element's value

   pq.insert(3);
   pq.insert(2);
   pq.insert(15);

   cout << "Size is " << pq.size() << endl;

   cout << pq.top() << " ";
   pq.deletes();

   cout << pq.top() << " ";
   pq.deletes();

   pq.insert(5);
   pq.insert(4);
   pq.insert(45);

   cout << endl << "Size is " << pq.size() << endl;

   cout << pq.top() << " ";
   pq.deletes();

   cout << pq.top() << " ";
   pq.deletes();

   cout << pq.top() << " ";
   pq.deletes();

   cout << pq.top() << " ";
   pq.deletes();

   cout << endl << std::boolalpha << pq.empty();

   return 0;
}

​​​​​​​

Kindly revert for any queries

Thanks.