【剑指Offer】29.最小的K个数（Python实现）

题目描述

输入n个整数，找出其中最小的K个数。例如输入4,5,1,6,2,7,3,8这8个数字，则最小的4个数字是1,2,3,4,。

解法一：分治法

class Solution:
    def GetLeastNumbers_Solution(self, tinput, k):
        n = len(tinput)
        if k <= 0 or k > n:
            return list()
        start = 0
        end = n - 1
        mid = self.partition(tinput, start, end)
        while k - 1 != mid:
            if k - 1 > mid:
                start = mid + 1
                mid = self.partition(tinput, start, end)
            elif k - 1 < mid:
                end = mid - 1
                mid = self.partition(tinput, start, end)
        res = tinput[:mid+1]
        res.sort()
        return res
        
    def partition(self, numbers, low, high):
        key = numbers[low]
        while low < high:
            while low < high and numbers[high] >= key:
                high -= 1
            numbers[low] = numbers[high]
            while low < high and numbers[low] <= key:
                low += 1
            numbers[high] = numbers[low]
        numbers[low] = key
        return low