Shubh Shubh - 1 year ago 88
C Question

Can someone improve my heap data structure code?

I am trying to build max heap from a random array so that i can get largest number in the root.

Also plese suggest me, how to get the size of the heap in the heapify() function.


int i;
void heapify(int a[],int i) //n=node at which heapify needs to apply
int size=8;
int max=i,l=2i,r=2i+1;
if(a[l]>a[max] && l<=size)
if(a[r]>a[max] && r<=size)
if(max==i) return;

//Using this function to call recursively heapify to maintain heap data structure
void build_heap(int arr[],int n) //n : size of array
for(i=floor(n/2);i>0;i--) // n/2 because after that every node is a leaf node and they follow heap property by default

int main()
int arr[] = {2,5,4,8,9,10,3,1};
printf("%d ",arr[i]);
return 0;

Answer Source

Your code seems to be fine except for a few changes:

  • Change 2i and 2i+1 to be 2*i and 2*i+1 otherwise you'll get a compilation error. Actually it should really be l = 2*i+1 and r = 2*i+2 because C arrays are 0-indexed. You are assuming 1-based indexing in your code.
  • In build_heap(), run the loop from [floor(n/2), 0] (you excluded 0'th element probably because of the reason stated in the above point).

You can pass the size of the heap as an argument to the heapify() function or declare it as a global variable (though it is advised to avoid global variables).

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