public class KuaiSu {
    public static void main(String []args){
        int[] a = {12,20,5,16,15,1,30,45,23,9};
        int low = 0;
        int high = a.length-1;
        paixu(a,low,high);
        for(int i = 0; i<a.length; i++){
             System.out.print(a[i]+",");
         }     
     }
    
    public static void paixu(int[] a,int low,int high){
        if(low<high){
            int key = sort(a,low,high);
            paixu(a,low,key-1);
            paixu(a,key+1,high);
        }
    }
     
     
    public static int sort(int[] a,int low,int high){
         int key = a[low];         
         while(high>low){
             //从后往前比较
             while(high>low&&a[high]>=key){  //若大于key移动位置
                 high--;
             }
             a[low]=a[high];  //不大于，交换两个值

             //从前往后比较
             while(high>low&&a[low]<=key){  //若小于key移动位置
                 low++;
             }
             a[high]=a[low];   //不小于，交换两个值
         }
         a[low]=key;
         return low;
        }
}