编程题目： 找出最小的k个数

找出最小或者最大的几个数我使用的是堆排序，效率为0（nlgn）

构建小顶堆返回末尾的k个数 或者 构建大顶堆返回前k个数

#!/usr/bin/env python3

def heap_sort(ary, num):
        def siftdown(ary, e, begin, end):
                i,j = begin, begin*2+1
                while j < end:
                        if j+1 < end and ary[j+1] < ary[j]:
                                j += 1
                        if e < ary[j]:
                                break
                        ary[i] = ary[j]
                        i,j = j,j*2+1
                ary[i] = e

        end = len(ary)
        for i in range(end//2-1, -1, -1):
                siftdown(ary, ary[i], i, end)

        #方法1
        for i in range(end-1, -1, -1):
                e = ary[i]
                ary[i] = ary[0]
                siftdown(ary, e, 0, i)
        return ary[:-num-1:-1]

        #方法2
        """
        li = []
        for i in range(num):
                if len(ary) > i:
                        li.append(ary[0])
                        e = ary[end-1-i]
                        siftdown(ary, e, 0, end-1-i)
                else:
                        break
        return li       
        """

if __name__ == '__main__':
        a = [4,5,1,6,2,7,3,8]
        num = int(input("最小的k个数:"))
        print(heap_sort(a,num))