Merge pull request keon#51 from ihchen/heap-sort

Heap Sort

Author: ankit167

sort/heap_sort.py

@@ -0,0 +1,93 @@
+def max_heap_sort(arr):
+    """ Heap Sort that uses a max heap to sort an array in ascending order
+        Complexity: O(n log(n))
+    """
+    for i in range(len(arr)-1,0,-1):
+        max_heapify(arr, i)
+        
+        temp = arr[0]
+        arr[0] = arr[i]
+        arr[i] = temp
+
+	
+def max_heapify(arr, end):
+    """ Max heapify helper for max_heap_sort
+    """
+    last_parent = int((end-1)/2)
+
+    # Iterate from last parent to first
+    for parent in range(last_parent,-1,-1):
+        current_parent = parent
+
+        # Iterate from current_parent to last_parent
+        while current_parent <= last_parent:
+            # Find greatest child of current_parent
+            child = 2*current_parent + 1
+            if child + 1 <= end and arr[child] < arr[child+1]:
+                child = child + 1
+
+            # Swap if child is greater than parent
+            if arr[child] > arr[current_parent]:
+                temp = arr[current_parent]
+                arr[current_parent] = arr[child]
+                arr[child] = temp
+
+                current_parent = child
+            # If no swap occured, no need to keep iterating
+            else:
+                break
+		
+
+def min_heap_sort(arr):
+    """ Heap Sort that uses a min heap to sort an array in ascending order
+        Complexity: O(n log(n))
+    """
+    for i in range(0, len(arr)-1):
+        min_heapify(arr, i)
+	
+
+def min_heapify(arr, start):
+    """ Min heapify helper for min_heap_sort
+    """
+    # Offset last_parent by the start (last_parent calculated as if start index was 0)
+    # All array accesses need to be offet by start
+    end = len(arr)-1
+    last_parent = int((end-start-1)/2)
+
+    # Iterate from last parent to first
+    for parent in range(last_parent,-1,-1):
+        current_parent = parent
+
+        # Iterate from current_parent to last_parent
+        while current_parent <= last_parent:
+            # Find lesser child of current_parent
+            child = 2*current_parent + 1
+            if child + 1 <= end-start and arr[child+start] > arr[child+1+start]:
+                child = child + 1
+
+            # Swap if child is less than parent
+            if arr[child+start] < arr[current_parent+start]:
+                temp = arr[current_parent+start]
+                arr[current_parent+start] = arr[child+start]
+                arr[child+start] = temp
+
+                current_parent = child
+            # If no swap occured, no need to keep iterating
+            else:
+                break
+
+if __name__ == '__main__':
+	import timeit
+
+	array = [1,5,65,23,57,1232,-1,-5,-2,242,100,4,423,2,564,9,0,10,43,64]
+	print("array:")
+	print(array)
+	print("Max Heapify:")
+	max_heap_sort(array)
+	print(array)
+	array = [1,5,65,23,57,1232,-1,-5,-2,242,100,4,423,2,564,9,0,10,43,64]
+	print("Min Heapify:")
+	min_heap_sort(array)
+	print(array)
+	print("Max Heapify Time:", timeit.timeit('max_heap_sort(array)', setup="from __main__ import max_heap_sort, array",number=10000))
+	print("Min Heapify Time:", timeit.timeit('min_heap_sort(array)', setup="from __main__ import min_heap_sort, array",number=10000))