Deleting in a Heap

Procedure :

• Copy the last element to root i.e index 1.

• Shift the root element to last element of heap.

• Set i as 1 (root) and j as 2*i (left child of root).

• Perform the following until j < size - 1.

• Find which of the child is greater.

• Set j to point on that child.

• If the child element (j) is greater than parent element (i), swap them.

• Set i as j and j as 2*j after each iteration.

int deleteFromHeap(int h[], int size) {

	// Copy last element to root and first element to last place
	int lastElement = h[size];
	int firstElement = h[1];
	h[1] = lastElement;
	h[size] = firstElement;

	// Keep i at root and j at left child of root initially
	int i = 1, j = 2*i;

	while(j < size-1) {

		// Find out if left child is greater or right child
		if (h[j+1] > h[j]) 
			j = j + 1;
	
		// If child is greater than parent, interchange
		if (h[j] > h[i]) {
			int temp = h[i];
			h[i] = h[j];
			h[j] = temp;
			// Set i to j and j to left child of j
			i = j;
			j = 2*j;
		} else {
			break;
		}
	}
	return firstElement;

}

By calling the same function n times, heap sort can be implemented.