最小的K个数

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,。

快速排序

import java.util.*;public class Solution {    public ArrayList<Integer> GetLeastNumbers_Solution(int [] input, int k) {        ArrayList<Integer> al=new ArrayList<Integer>();        if(input.length < k || k <= 0||input.length ==0)            return al;        int low=0;        int high=input.length-1;        int index=partition(input,low,high);        while(index!=k-1){            if(index>k-1){                high=index-1;                index=partition(input,low,high);            }            else{                low=index+1;                index=partition(input,low,high);            }         }        for(int i=0;i<k;i++){            al.add(input[i]);        }        return al;    }    public static int partition(int[] data,int low,int high){        int temp=data[low];        while(low<high){            while(temp<=data[high]&&low<high){                high--;            }            data[low]=data[high];            while(temp>=data[low]&&low<high){                low++;            }            data[high]=data[low];        }        data[low]=temp;        return low;    }}