Main.java

import java.io.*;

class Main{
  private static void quickSort(int[] a, int left, int right){
    if(left < right){
      int pivot;
      { // partition
        int x, i, j;
        x = a[left];
        i = left - 1;
        j = right + 1;
        while(true){
          do j--; while(a[j]>x);
          do i++; while(a[i]<x);
          if(i < j){ // swap
            int tmp = a[i];
            a[i] = a[j];
            a[j] = tmp;
          }else{
            pivot = j;
            break;
          }
        }
      }
      quickSort(a, left, pivot);
      quickSort(a, pivot+1, right);
    }
  }

  static void sortArray(int[] a){
    quickSort(a, 0, a.length-1);
  }

  static void printArray(int[] a){
    for(int i=0; i<a.length; i++)
      System.out.print(" " + a[i]);
    System.out.println();
  }

  public static void main(String[] args){
    int[] a = { 3, 2, 6, 1, 2, 0, 7 };
    printArray(a);
    sortArray(a);
    printArray(a);
  }
}