package sort;


public class QuickSort {
    
    private static void exch(int[] a,int i,int j){
        int t=a[i];
        a[i]=a[j];
        a[j]=t;
}
    
    private static int partition(int[] a,int lo,int hi){
        int i=lo,j=hi+1;
        int v=a[lo];
        while(true){
            while(a[++i]<v)
                if(i==hi)
                    break;
            while(a[--j]>v)
                if(j==lo)
                    break;
            if(i>=j)
                break;
            exch(a,i,j);
        }
        exch(a,lo,j);
        return j;
    }
    private static void sort(int[] a, int lo,int hi){
        if(hi<=lo)
            return;
        int j=partition(a,lo,hi);
        sort(a,lo,j-1);
        sort(a,j+1,hi);
    }
    public void sort(int[] a){
        sort(a,0,a.length-1);
    }
}