C++ Program to Implement Min Heap

A Binary Heap is a complete binary tree which is either Min Heap or Max Heap. In a Max Binary Heap, the key at root must be maximum among all keys present in Binary Heap. This property must be recursively true for all nodes in Binary Tree. Min Binary Heap is similar to Min Heap.

Algorithm

For min_heap():

Begin
   Declare function min_heap(int *a, int m, int n)
      Declare j, t of the integer datatype.
      Initialize t = a[m].
      j = 2 * m;
      while (j <= n) do
         if (j < n && a[j+1] < a[j]) then
            j = j + 1
         if (t < a[j]) then
            break
         else if (t >= a[j]) then
            a[j / 2] = a[j]
            j = 2 * j
      a[j/2] = t
   return
End.

For build_minheap:

Begin
   Declare function build_minheap(int *a,int n).
      Declare k of the integer datatype.
      for(k = n/2; k >= 1; k--)
         Call function min_heap(a,k,n)
End.

Example

#include <iostream>
#include <conio.h>
using namespace std;
void min_heap(int *a, int m, int n){
   int j, t;
   t= a[m];
   j = 2 * m;
   while (j <= n) {
      if (j < n && a[j+1] < a[j])
         j = j + 1;
      if (t < a[j])
         break;
      else if (t >= a[j]) {
         a[j/2] = a[j];
         j = 2 * j;
      }
   }
   a[j/2] = t;
   return;
}
void build_minheap(int *a, int n) {
   int k;
   for(k = n/2; k >= 1; k--) {
      min_heap(a,k,n);
   }
}
int main() {
   int n, i;
   cout<<"enter no of elements of array\n";
   cin>>n;
   int a[30];
   for (i = 1; i <= n; i++) {
      cout<<"enter element"<<" "<<(i)<<endl;
      cin>>a[i];
   }
   build_minheap(a, n);
   cout<<"Min Heap\n";
   for (i = 1; i <= n; i++) {
      cout<<a[i]<<endl;
   }
   getch();
}

Output

enter no of elements of array
5
enter element 1
7
enter element 2
6
enter element 3
2
enter element 4
1
enter element 5
4
Min Heap
1
4
2
6
7