Editing Heapsort (section)

=== Standard implementation ===
Although it is convenient to think of the two phases separately, most implementations combine the two, allowing a single instance of {{code|siftDown}}to be [[Inline expansion|expanded inline]].<ref>{{harvnb|Knuth|1997}}</ref>{{rp|Algorithm H}}  Two variables (here, {{code|start}} and {{code|end}}) keep track of the bounds of the heap area.  The portion of the array before {{code|start}} is unsorted, while the portion beginning at {{code|end}} is sorted.  Heap construction decreases {{code|start}} until it is zero, after which heap extraction decreases {{code|end}} until it is 1 and the array is entirely sorted.

 '''procedure''' heapsort(a, count) '''is'''
     '''input:''' an unordered array ''a'' of length ''count''
     
     start ← floor(count/2)
     end ← count
     '''while''' end > 1 '''do'''
         '''if''' start > 0 '''then'''    ''(Heap construction)''
             start ← start − 1
         '''else'''                 ''(Heap extraction)''
             end ← end − 1
             swap(a[end], a[0])
    
         ''(The following is siftDown(a, start, end))''
         root ← start
         '''while''' iLeftChild(root) < end '''do'''
             child ← iLeftChild(root)
             ''(If there is a right child and that child is greater)''
             '''if''' child+1 < end '''and''' a[child] < a[child+1] '''then'''
                 child ← child + 1
     
             '''if''' a[root] < a[child] '''then'''
                 swap(a[root], a[child])
                 root ← child         ''(repeat to continue sifting down the child now)''
             '''else'''
                 '''break'''                ''(return to outer loop)''