30일: 빠른 정렬

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.Random;



public class Day30 {

    static int partition(int[] array, int low, int high) {

        int j, temp, i = low + 1;

        Random random = new Random();

        int x = random.nextInt(high - low) + low;

        temp = array[low];

        array[low] = array[x];

        array[x] = temp;

        for (j = low + 1; j <= high; j++) {

            if (array[j] <= array[low] && j != i) {

                temp = array[j];

                array[j] = array[i];

                array[i++] = temp;

            } else if (array[j] <= array[low]) {

                i++;

            }

        }

        temp = array[i - 1];

        array[i - 1] = array[low];

        array[low] = temp;

        return i - 1;

    }

    static void Day30(int[] array,int low,int high){

        if(low<high){

            int mid = partition(array,low,high);

            Day30(array,low,mid-1);

            Day30(array,mid+1,high);

        }

    }

    public static void main(String[] args) {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        int size;

        System.out.println("Enter the size of the array");

        try {

            size = Integer.parseInt(br.readLine());

        } catch (Exception e) {

            System.out.println("Invalid Input");

            return;

        }

        int[] array = new int[size];

        System.out.println("Enter array elements");

        int i;

        for (i = 0; i < array.length; i++) {

            try {

                array[i] = Integer.parseInt(br.readLine());

            } catch (Exception e) {

                System.out.println("Error");

            }

        }

        System.out.println("The initial array is");
        System.out.println(Arrays.toString(array));
        Day30(array,0,array.length-1);
        System.out.println("The sorted array is");
        System.out.println(Arrays.toString(array));

    }

}