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Task/Sorting-algorithms-Heapsort/Liberty-BASIC/sorting-algorithms-heapsort.liberty

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+wikiSample=1    'comment out for random array
+
+data 6, 5, 3, 1, 8, 7, 2, 4
+    itemCount = 20
+if wikiSample then itemCount = 8
+    dim A(itemCount)
+    for i = 1 to itemCount
+        A(i) = int(rnd(1) * 100)
+        if wikiSample then read tmp: A(i)=tmp
+    next i
+
+    print "Before Sort"
+    call printArray itemCount
+
+    call heapSort itemCount
+
+    print "After Sort"
+    call printArray itemCount
+end
+
+'------------------------------------------
+sub heapSort count
+    call heapify count
+
+    print "the heap"
+    call printArray  count
+
+    theEnd = count
+    while theEnd > 1
+        call swap theEnd, 1
+        call siftDown 1, theEnd-1
+        theEnd = theEnd - 1
+    wend
+end sub
+
+sub heapify count
+    start = int(count / 2)
+    while start >= 1
+         call siftDown start, count
+         start = start - 1
+    wend
+end sub
+
+sub siftDown start, theEnd
+    root = start
+    while root * 2 <= theEnd
+        child = root * 2
+        swap = root
+        if A(swap) < A(child) then
+            swap = child
+        end if
+        if child+1 <= theEnd  then
+            if A(swap) < A(child+1) then
+                swap = child + 1
+            end if
+        end if
+        if swap <> root then
+            call swap root, swap
+            root = swap
+        else
+            exit sub
+        end if
+    wend
+end sub
+
+sub swap a,b
+    tmp = A(a)
+    A(a) = A(b)
+    A(b) = tmp
+end sub
+
+'===========================================
+sub printArray itemCount
+    for i = 1 to itemCount
+        print using("###", A(i));
+    next i
+    print
+end sub