洗一个select函数demo
时间: 2023-12-04 18:01:35 浏览: 27
好的,以下是一个简单的select函数demo:
```python
import random
import time
def select(array, k):
if len(array) == 1:
return array[0]
pivot = random.choice(array)
left = []
right = []
pivots = []
for x in array:
if x < pivot:
left.append(x)
elif x > pivot:
right.append(x)
else:
pivots.append(x)
if k < len(left):
return select(left, k)
elif k < len(left) + len(pivots):
return pivots[0]
else:
return select(right, k - len(left) - len(pivots))
start_time = time.time()
array = [5, 3, 9, 1, 7, 2]
k = 3
result = select(array, k)
print(f"The {k}th smallest element in {array} is {result}")
print(f"Execution time: {time.time() - start_time:.6f} seconds")
```
这个demo实现了一个选择算法(select algorithm),用于在一个未排序的数组中找到第k小的元素。它的时间复杂度为O(n),比快速排序的O(nlogn)更快,因为它不需要对整个数组进行排序。