划分算法

package sy;

class ArrayPar{
    private long[] theArray;
    private int nElems;
    
    public ArrayPar(int max){
        theArray = new long[max];
        nElems = 0;
    }
    
    public void insert(long value){
        theArray[nElems] = value;
        nElems ++;
    }
    
    public int size(){
        return nElems;
    }
    public void display(){
        System.out.print("A = ");
        for(int j = 0; j < nElems; j++)
        {
            System.out.print(theArray[j] + " ");
        }
        System.out.print("");
    }
    
    public int partitionIt(int left,int right,long value)
    {
        //定义左指针，因为内层while的theArray[++leftPtr]先自增了，所以这里先减一
        int leftPtr = left - 1;
        //定义有指针，以为内层while的theArray[++leftPtr]先自减，这里先加一
        int rightPtr = right + 1;
        while(true)
        {
            //内层俩个while循环目的是选择交换项
            while(leftPtr < right && theArray[++leftPtr] < value)
            {
                
            }
            while(rightPtr > left && theArray[--rightPtr] > value)
            {
                
            }
            //如果俩个指针相遇，则停止划分，划分结束
            if(leftPtr >= rightPtr)
            {
                break;
            }
            else
            {
                //交换
                long temp = theArray[leftPtr];
                theArray[leftPtr] = theArray[rightPtr];
                theArray[rightPtr] = temp;
            }
            
        }
        return leftPtr;
    }
}

class App{
    public static void main(String[] args)
    {
        int maxSize = 16;
        ArrayPar arr;
         arr = new ArrayPar(maxSize);
        
        for(int j = 0; j < maxSize; j++)
        {
            long n = (int)(java.lang.Math.random()*199);
            arr.insert(n);
        }
        arr.display();
        long pivot = 99;
        System.out.print("Pivot is " +pivot);
        int size = arr.size();
        int partDex = arr.partitionIt(0, size - 1, pivot);
        System.out.println(",Partition is at index" + partDex);
        arr.display();    
    }
}