all tasks

Task/Sorting-algorithms-Heapsort/Pascal/sorting-algorithms-heapsort.pascal

@@ -0,0 +1,77 @@
+program HeapSortDemo;
+
+type
+  TIntArray = array[4..15] of integer;
+
+var
+  data: TIntArray;
+  i: integer;
+
+procedure siftDown(var a: TIntArray; start, ende: integer);
+  var
+    root, child, swap: integer;
+  begin
+    root := start;
+    while root * 2 - start + 1 <= ende do
+    begin
+      child := root * 2 - start + 1;
+      if (child + 1 <= ende) and (a[child] < a[child + 1]) then
+        inc(child);
+      if a[root] < a[child] then
+      begin
+	swap     := a[root];
+        a[root]  := a[child];
+        a[child] := swap;
+        root := child;
+      end
+      else
+        exit;
+    end;
+  end;
+
+procedure heapify(var a: TIntArray);
+  var
+    start, count: integer;
+  begin
+    count := length(a);
+    start := low(a) + count div 2 - 1;
+    while start >= low(a) do
+    begin
+      siftdown(a, start, high(a));
+      dec(start);
+    end;
+  end;
+
+procedure heapSort(var a: TIntArray);
+  var
+    ende, swap: integer;
+  begin
+    heapify(a);
+    ende := high(a);
+    while ende > low(a) do
+    begin
+      swap := a[low(a)];
+      a[low(a)] := a[ende];
+      a[ende] := swap;
+      dec(ende);
+      siftdown(a, low(a), ende);
+    end;
+  end;
+
+begin
+  Randomize;
+  writeln('The data before sorting:');
+  for i := low(data) to high(data) do
+  begin
+    data[i] := Random(high(data));
+    write(data[i]:4);
+  end;
+  writeln;
+  heapSort(data);
+  writeln('The data after sorting:');
+  for i := low(data) to high(data) do
+  begin
+    write(data[i]:4);
+  end;
+  writeln;
+end.