python实现堆排序的三种方式

标签：堆排序   python   

# -*- coding: utf-8 -*-
"""
Created on Fri May 16 14:57:50 2014

@author: lifeix
"""
import heapq
#堆排序
#第一种实现
def Heapify(a, start, end):
    left = 0
    right = 0
    maxv = 0
    left = start * 2
    right = start * 2 + 1
    while left <= end:
        maxv = left
        if right <= end:
            if a[left] < a[right]:
                maxv = right
            else:
                maxv = left
        if a[start] < a[maxv]:
            a[maxv],a[start] = a[start],a[maxv]
            start = maxv
        else:
            break
        left = start * 2
        right = start * 2 + 1
        
def BuildHeap(a):
    size = len(a)
    i = (size -1) // 2;
    while i >= 0:
        Heapify(a, i, size - 1)
        i = i - 1
        
def HeapSort(a):
    BuildHeap(a)
    print ‘first before sorted:‘, a
    i = len(a) - 1
    
    while i >= 0:
        a[0],a[i] = a[i],a[0]
        Heapify(a, 0, i - 1)
        i = i - 1
        
a = [4,1,3,2,16,9,10,14,8,7]
HeapSort(a)
print ‘first after sorted‘,a

#第二种实现
def buildHeap(a,size):
    for j in range(size/2 - 1, -1,-1):
        adjustHeap(a,j,size)
    
def adjustHeap(a, i, size):
    lchild = 2*i  #i的左孩子节点序号
    rchild = 2*i + 1 #i的右孩子节点序号
    maxIndex = i
    if i < size/2:
        if lchild <= size and a[lchild] > a[maxIndex]:
            maxIndex = lchild
        if rchild <= size and a[rchild] > a[maxIndex]:
            maxIndex = rchild
        if maxIndex != i:
            a[i],a[maxIndex] = a[maxIndex], a[i]
            adjustHeap(a, maxIndex,size)
    

if __name__ == "__main__":
   a =[4,1,3,2,16,9,10,14,8,7]
   b =[4,1,3,2,16,9,10,14,8,7]
   buildHeap(a, len(a))
   print ‘-------------------------------------------------‘
   print ‘second before sorted‘,a
   i = len(a) - 1
   while i >= 0:
       a[0],a[i] = a[i],a[0]
       buildHeap(a,i)
       i = i - 1
   print ‘second after sorted‘,a
   
   #python自带函数实现
   heapq.heapify(b)
   heap = []
   while b:
        heap.append(heapq.heappop(b))
   b[:] = heap
   print ‘-------------------------------------------------‘
   print ‘sdk sorted‘,b
        

python实现堆排序的三种方式,布布扣,bubuko.com

python实现堆排序的三种方式

标签：堆排序   python   

原文地址：http://blog.csdn.net/startupmount/article/details/25983393