# 6. 三向切分快速排序

java

```java
//排序抽象类
public abstract class Sort<T extends Comparable<T>> {
    public abstract void sort(T[] nums);

    public boolean less(T v,T w){
        return v.compareTo(w)<0;
    }

    public void swap(T[] a,int i,int j){
        T t=a[i];
        a[i]=a[j];
        a[j]=t;
    }
}

//快速排序，继承排序
public class QuickSort<T extends Comparable<T>> extends Sort<T> {
    @Override
    public void sort(T[] nums) {
        shuffle(nums);
        sort(nums,0,nums.length-1);
    }

    public void sort(T[] nums,int l,int h){
        if(l>=h) return;
        int j=partition(nums,l,h);
        sort(nums,l,j-1);
        sort(nums,j+1,h);
    }

    public int partition(T[] nums,int l,int h){
        int i=l,j=h+1;
        T v=nums[l];
        while(true){
            while(j!=l&&less(v,nums[--j]));
            while(i!=h&&less(nums[++i],v));
            if(i>=j) break;
            swap(nums,i,j);
        }
        swap(nums,l,j);
        return j;
    }

    public void shuffle(T[] nums){
        List<Comparable> list=Arrays.asList(nums);
        Collections.shuffle(list);
        list.toArray(nums);
    }
}

// 三切分快速排序，继承快速排序
public class ThreeWayQuickSort<T extends Comparable<T>> extends QuickSort<T> {
    @Override
    public void sort(T[] nums, int l, int h) {
        if(l>=h) return;
        int lt=l,i=l+1,gt=h;
        T v=nums[l];
        System.out.println(v);
        while (i<=gt){
            int compare=nums[i].compareTo(v);
            if(compare<0){
                swap(nums,lt++,i++);
            }else if(compare>0){
                swap(nums,i,gt--);
            }else {
                i++;
            }
        }
        sort(nums,l,lt-1);
        sort(nums,gt+1,h);
    }

    public static void main(String[] args){
        Integer[] arr={
                5,1,8,1,3,3,3,3,5,5,8,8,8
        };
        ArrayUtils.printArray(arr);
        Sort<Integer> sort=new ThreeWayQuickSort<>();
        sort.sort(arr);
        ArrayUtils.printArray(arr);
    }
}
```


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