Algorithm for creating min-heap

Question

I got this question in an exam, but I'm not sure that I understand what it wants me to do. Can you please clarify that if I did the correct thing?

An integer array A is passed to the function makeHeap . if A[0] contains n, then A[1] to A[n-1] contain numbers in arbitrary order. Write makeHeap such that A[1] to A[n-1] contain a min-heap. Your function must create the heap by processing the elements in the order A[2] , A[3] ,... , A[n-1].

void makeHeap(int A[], int n)
{
  int r = n -1 ; 
  for(int i = 1; i <= n/2; i++)
    siftUp(a, i , r );
}

/* i- parent , r - right of the array */ 
void siftUp(int A[], int i , int r )
{
   boolean done = false ; 
   int j = 2* i ; 
   while (j <= r && !done)
   {
     if(A[j] > A[j+1]) // find the smalest child
       j+=1 ; 
     if(A[i] > A[j])
     {
       // code to swap A[i] and A[j]
       i = j ; 
       j = i*2 ;

     } 
     else done = true ; 
   }
}

Is this solution even remotely correct? Also, is siftUp the correct name of the function?

Edit:

void makeHeap(int A[], int n)
{ 
  for(int i = 1; i <= A[0]/2; i++)
    siftUp(A, i );
}

/* i- parent */ 
void siftUp(int A[], int i )
{
   bool done = false ; 
   int j = 2* i ; 
   while (i > 1 && !done)
   {
     if(A[j] > A[j+1]) // find the smallest child
       j+=1 ; 
     if(A[i] > A[j])
     {
       /* swap A[j] and A[i] */
       int temp = A[i]; 
       A[i] = A[j]; 
       A[j] = temp ; 

       j = i ; 
       i = i / 2 ; 


     } 
     else done = true ; 
   }
}

Answer 1

Your code wouldn't heapify the array (ignoring errors like a and boolean )

For siftUp(), bear in mind the property parent(i) = i/2 , where i is a node's index. Some pseudocode for inserting node into the heap (as the last node of the heap):

 Algo siftUp(H[], n)
     i = n
     while i > 1 and H[i] < H[i/2]
         swap(H[i], H[i/2])
         i = i / 2

This would result in O(nlogn) as you iterate through the array, but there is a better approach with the bottom up construction with O(n).