mirror of
https://github.com/heqin-zhu/algorithm.git
synced 2024-03-22 13:30:46 +08:00
96 lines
2.9 KiB
Python
96 lines
2.9 KiB
Python
def quickSort(lst):
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'''A optimized version of Hoare partition'''
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def partition(a,b):
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pivot = lst[a]
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while a!=b:
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while a<b and lst[b]>pivot: b-=1
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if a<b:
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lst[a] = lst[b]
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a+=1
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while a<b and lst[a]<pivot: a+=1
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if a<b:
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lst[b] = lst[a]
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b-=1
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lst[a] = pivot
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return a
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def _sort(a,b):
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if a>=b:return
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mid = (a+b)//2
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# 三数取中值置于第一个作为 pivot
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if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[a],lst[mid] = lst[mid],lst[a] # lst[mid] 为中值
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if (lst[a]<lst[b]) ^ (lst[b]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
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i = partition(a,b)
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_sort(a,i-1)
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_sort(i+1,b)
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_sort(0,len(lst)-1)
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return lst
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def quickSort2(lst):
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'''A version of partition from <Introduction of Algorithm>, a little bit slow'''
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def partition(a,b):
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pivot = lst[b]
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j = a-1
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for i in range(a,b):
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if lst[i]<=pivot:
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j+=1
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if i!=j: lst[i], lst[j] = lst[j], lst[i]
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lst[j+1],lst[b] = lst[b],lst[j+1]
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return j+1
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def _sort(a,b):
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if a>=b:return
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mid = (a+b)//2
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# 三数取中值置于第一个作为 pivot
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if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[b],lst[mid] = lst[mid],lst[b] # lst[mid] 为中值
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if (lst[a]>lst[b]) ^ (lst[a]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
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i = partition(a,b)
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_sort(a,i-1)
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_sort(i+1,b)
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_sort(0,len(lst)-1)
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return lst
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def quickSort3(lst):
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'''A rear recursive optimization version'''
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def partition(a,b):
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pivot = lst[b]
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j = a-1
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for i in range(a,b):
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if lst[i]<=pivot:
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j+=1
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if i!=j: lst[i], lst[j] = lst[j], lst[i]
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lst[j+1],lst[b] = lst[b],lst[j+1]
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return j+1
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def _sort(a,b):
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while a<b:
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mid = (a+b)//2
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# 三数取中值置于第一个作为 pivot
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if (lst[a]<lst[mid]) ^ (lst[b]<lst[mid]): lst[b],lst[mid] = lst[mid],lst[b] # lst[mid] 为中值
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if (lst[a]>lst[b]) ^ (lst[a]>lst[mid]): lst[a],lst[b] = lst[b],lst[a] # lst[b] 为中值
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i = partition(a,b)
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_sort(a,i-1)
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a = i+1
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_sort(0,len(lst)-1)
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return lst
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from time import time
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def timer(func,lst,n=100):
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t = time()
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for i in range(n):func(lst)
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t = time()-t
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print('{}: {}s'.format(func.__name__,t))
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return t
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if __name__ == '__main__':
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from random import randint
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print('5000 items, repeat 100 times for each')
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lst = [randint(0,100) for i in range(5000)]
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timer(quickSort,lst.copy())
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timer(quickSort2,lst.copy())
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timer(quickSort3,lst.copy())
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lst = [randint(0,100) for i in range(15)]
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print(lst)
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print(quickSort(lst.copy()))
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print(quickSort2(lst.copy()))
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print(quickSort3(lst.copy()))
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