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Task/Sorting-algorithms-Heapsort/Nim/sorting-algorithms-heapsort.nim

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+proc siftDown[T](a: var openarray[T]; start, ending: int) =
+  var root = start
+  while root * 2 + 1 < ending:
+    var child = 2 * root + 1
+    if child + 1 < ending and a[child] < a[child+1]:
+      inc child
+    if a[root] < a[child]:
+      swap a[child], a[root]
+      root = child
+    else:
+      return
+
+proc heapSort[T](a: var openarray[T]) =
+  let count = a.len
+  for start in countdown((count - 2) div 2, 0):
+    siftDown(a, start, count)
+  for ending in countdown(count - 1, 1):
+    swap a[ending], a[0]
+    siftDown(a, 0, ending)
+
+var a = @[4, 65, 2, -31, 0, 99, 2, 83, 782]
+heapSort a
+echo a