Heap Sort

1
Heap Sort

• Panickos Neophytou
• Recitation 2 09/19/2005
• 09/21/2005

CS0447 Computer Organization and Assembly Link
for this presentation www.cs.pitt.edu/panickos/c
ourses/cs0447/heapsort.ppt
2
Heap

• Definition A heap is a list in which each
  element contains a key, such that the key in the
  element at position k in the list is at least as
  large as the key in the element at position 2k
  1 (if it exists), and 2k 2 (if it exists)

3
Heap
4
Heap sort pseudocode

• function heapSort(a, count)
• var int start count 2 - 1, end count - 1
  
• while start 0
• sift(a, start, count)
• start start 1
• while end gt 0
• swap(aend, a0)
• sift(a, 0, end)
• end end - 1
• function sift(a, start, count)
• var int root start, child
• while root 2 1 lt count
• child root 2 1
• if child lt count - 1 and achild lt achild
  1
• child child 1

5
Building a Heap

• Build Heap
• The above list is not a heap. Lets see how to
  build it into a heap

6
Building a Heap
7
Building a Heap
8
Building a Heap
9
Building a Heap
10
Building a Heap

• Now, the list becomes a heap

11
Fibonacci

• Write a recursive assembly program that
  calculates the Fibonacci numbers for a given
  integer n