目标：在一组数a0,a1,a2,a3,a4,a5,a6,a7,a8,a9中尽量取其中间值，以此为pivot，值大于pivot的元素置于pivot左边，反之至于右边。

源代码：

package com.paixu;

public class ArrayPar {

private int nElems;

private long[] arr;

public ArrayPar(int max){

arr = new long[max];

nElems =0;

}

public void insert(long value){

arr[nElems++] = value;

}

public void display(){

for(int i=0;i<nElems;i++)

System.out.print("the" + i + "Elem is " + arr[i] + " " );

}

public int size(){

return nElems;

}

public int partitionIt(int left,int right,int pivot){

int leftPtr = left -1;

int rightPtr = right + 1;

while(true){

while(leftPtr < right && arr[++leftPtr] < pivot)

;

while(rightPtr > left && arr[--rightPtr] > pivot)

;

if(leftPtr >= rightPtr)

break;

else

swap(leftPtr,rightPtr);

}

return leftPtr;

}

public void swap(int leftValue,int rightValue){

long temp;

temp =arr[rightValue];

arr[rightValue] = arr[leftValue];

arr[leftValue] = temp;

}

}

 

 

package com.paixu;

public class PartitionApp {

public static void main(String[] args){

int maxSize = 20;

ArrayPar arr = new ArrayPar(maxSize);

for(int i=0;i<maxSize;i++){

long n = (long)(Math.random() * 99);

arr.insert(n);

}

arr.display();

System.out.println();

int pivor = 50;

int size = arr.size();

int partDex = arr.partitionIt(0, size-1, pivor);

System.out.println("Partition is at index " + partDex);

arr.display();

}

}