Python实现插入算法、希尔排序、快速排序、归并排序_python 希尔排序归并排序-优快云博客

本文深入讲解了四种排序算法：插入排序、希尔排序、快速排序和归并排序。通过实例演示了每种算法的工作原理和步骤，帮助读者理解不同排序算法的特点和适用场景。

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#插入算法

	# def insert_sort(alist):
	#     i = 1
	#     for j in range(1,len(alist)):
	#         i = j
	#         while i > 0 :
	#
	#             if alist[i]<alist[i-1]:
	#                 alist[i],alist[i-1]=alist[i-1],alist[i]
	#                 i-=1
	#             else:
	#                 break
	#
	# if __name__=="__main__":
	#     li = [54,26,93,17,77,31,44,55,20]
	#     print(li)
	#     insert_sort(li)
	#     print(li)

# 希尔排序

	# def shell_sort(alist):
	#     n = len(alist)
	#     gap = n//2
	#     while gap > 0:
	#         for j in range(gap, n):
	#             i = j
	#             while i > 0 :
	#                 if alist[i]<alist[i-gap]:
	#                     alist[i],alist[i-gap]=alist[i-gap],alist[i]
	#                     i-=gap
	#                 else:
	#                     break
	#         gap//=2
	#
	# if __name__=="__main__":
	#     li = [54,26,93,17,77,31,44,55,20]
	#     print(li)
	#     shell_sort(li)
	#     print(li)

快速排序

def quick_sort(alist,first,last):
    if first>=last:
        return
    n = len(alist)
    mid_value = alist[first]
    low = first
    high = last

    while low < high:
        while low<high and alist[high]>mid_value:
            high-=1
        alist[low] = alist[high]

        while low<high and alist[low]<mid_value:
            low +=1
        alist[high] = alist[low]
    alist[low] = mid_value

    quick_sort(alist,first,low-1)
    quick_sort(alist,low+1,last)

if __name__=="__main__":
    li = [54,26,93,17,77,31,44,55,20]
    print(li)
    quick_sort(li,0,len(li)-1)
    print(li)

# 归并排序

# def merge_sort(alist):
#     n = len(alist)
#     if n<=1:
#         return alist
#     mid = n//2
#     left_li = merge_sort(alist[:mid])
#     right_li = merge_sort(alist[mid:])
#     left_pointer,right_pointer = 0,0
#     result = []
#     while left_pointer < len(left_li) and right_pointer < len(right_li):
#         if left_li[left_pointer] < right_li[right_pointer]:
#             result.append(left_li[left_pointer])
#             left_pointer+=1
#         else:
#             result.append(right_li[right_pointer])
#             right_pointer+=1
#     result+=left_li[left_pointer:]
#     result+=right_li[right_pointer:]
#     return result
#
# if __name__=="__main__":
#     li = [54,26,93,17,77,31,44,55,20]
#     print(li)
#     sorted_li = merge_sort(li)
#     print(sorted_li)