快速排序一（划分）

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();
}

}