Python实现二分查找

最新推荐文章于 2024-02-22 17:07:46 发布

OliverkingLi

最新推荐文章于 2024-02-22 17:07:46 发布

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分类专栏： python 文章标签： python 查找二分查找算法数据结构

本文链接：https://blog.youkuaiyun.com/OliverkingLi/article/details/80884125

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本文介绍了一种简单的顺序查找排序方法及两种二分查找排序方法的实现。通过定义类Sort并使用其内部方法order_sort、binary_sort1和binary_sort2来演示如何在列表中找到指定元素的位置。这些方法适用于已排序的列表，并返回查找成功与否的标志及元素位置。

class Sort:
	def __init__(self):
		pass

	def order_sort(self, lst, elem):
		pos = 0
		flag = False

		while pos < len(lst) and not flag:
			if elem == lst[pos]:
				flag = True
				return flag, pos+1
			else:
				pos += 1
		return flag, pos+1

	def binary_sort1(self, lst, elem):
		mid = None
		flag = False

		first = 0
		last = len(lst) - 1

		while first<=last and not flag:
			mid = (first + last) // 2
			if lst[mid] == elem:
				flag = True
			else:
				if lst[mid] > elem:
					last = mid - 1
				else:
					first = mid + 1
		print("mid", mid)
		if mid >= len(lst)-1 and not flag:
			mid = None
		else:
			mid += 1
		return flag, mid
	
	def binary_sort2(self, lst, elem):
		mid = None
		flag = False

		first = 0
		last = len(lst) - 1

		if len(lst) == 0:
			return False
		else:
			mid = (first + last) // 2
			if lst[mid] == elem:
				flag = True
				return flag
			else:
				if lst[mid] > elem:
					return self.binary_sort2(lst[:mid], elem)
				else:
					return self.binary_sort2(lst[mid+1:], elem)


if __name__ == '__main__':
	s = Sort()
	lst = [1,2,3,4]
	elem = 3
	flag, pos = s.order_sort(lst, elem)
	print(flag)
	print(pos)

	flag, pos = s.binary_sort1(lst, elem)
	print(flag)
	print(pos)

	flag = s.binary_sort2(lst, elem)
	print(flag)
	print(pos)