python 堆排序

堆的定义：
1、完全二叉树
2、父节点的值大于等于字节的的值(大顶堆)

# heapify功能：递归完成当前节点以及当前的节点的子节点堆的调整（父节点大于子节点）
def heapify(arr, n, i): 
    largest = i  
    l = 2 * i + 1     # left = 2*i + 1 
    r = 2 * i + 2     # right = 2*i + 2 
  
    if l < n and arr[i] < arr[l]: 
        largest = l 
  
    if r < n and arr[largest] < arr[r]: 
        largest = r 
  
    if largest != i: 
        arr[i],arr[largest] = arr[largest],arr[i]  # 交换
  
        heapify(arr, n, largest) 
  
def heapSort(arr): 
    n = len(arr) 
  
    # Build a maxheap. 
    for i in range(n, -1, -1): 
        heapify(arr, n, i) 
  
    # 一个个交换元素
    for i in range(n-1, 0, -1): 
        arr[i], arr[0] = arr[0], arr[i]   # 交换
        heapify(arr, i, 0) 
  
arr = [ 12, 11, 13, 5, 6, 7] 
heapSort(arr) 
n = len(arr) 
print ("排序后") 
for i in range(n): 
    print ("%d" %arr[i]),

参考：
https://www.cnblogs.com/shengyang17/p/13362354.html
https://blog.csdn.net/chibangyuxun/article/details/53018294
https://blog.csdn.net/qq_34840129/article/details/80638225