堆排序的Python程序

堆排序是一种基于二叉堆数据结构的比较排序技术。它类似于我们首先找到最大元素并将最大元素放在最后的选择排序。我们对剩余的元素重复相同的过程。

# Python program for implementation of heap Sort
  
# To heapify subtree rooted at index i.
# n is size of heap
def heapify(arr, n, i):
    largest = i  # Initialize largest as root
    l = 2 * i + 1     # left = 2*i + 1
    r = 2 * i + 2     # right = 2*i + 2
  
    # See if left child of root exists and is
    # greater than root
    if l < n and arr[i] < arr[l]:
        largest = l
  
    # See if right child of root exists and is
    # greater than root
    if r < n and arr[largest] < arr[r]:
        largest = r
  
    # Change root, if needed
    if largest != i:
        arr[i],arr[largest] = arr[largest],arr[i]  # swap
  
        # Heapify the root.
        heapify(arr, n, largest)
  
# The main function to sort an array of given size
def heapSort(arr):
    n = len(arr)
  
    # Build a maxheap.
    # Since last parent will be at ((n//2)-1) we can start at that location.
    for i in range(n // 2 - 1, -1, -1):
        heapify(arr, n, i)
  
    # One by one extract elements
    for i in range(n-1, 0, -1):
        arr[i], arr[0] = arr[0], arr[i]   # swap
        heapify(arr, i, 0)
  
# Driver code to test above
arr = [ 12, 11, 13, 5, 6, 7]
heapSort(arr)
n = len(arr)
print ("Sorted array is")
for i in range(n):
    print ("%d" %arr[i]),
# This code is contributed by Mohit Kumra

输出：

Sorted array is
5 6 7 11 12 13

有关更多详细信息，请参阅有关堆排序的完整文章！

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