java描写的合并排序的递归实现

package com.stu.find;

 

public class MergeSort {

    public   void  merge(int []A,int p,int q,int r)

    {

        int nl=q-p+1;

        int nr=r-q;

        int [] rArr=new int[nl+1];

        int [] lArr=new int [nr+1];

 

        for(int i=0;i<nl;i++)

        {

            rArr[i]=A[i+p];

        }

 

        for(int j=0;j<nr;j++)

        {

            lArr[j]=A[j+q+1];

        }

 

 

        rArr[nl] = Integer.MAX_VALUE; 

        lArr[nr] = Integer.MAX_VALUE; 

        int n=0;

        int m=0;

        //接下来进行比较

        for(int i=p;i<=r;i++)

        {

            if(m<=nl&&n<=nr)

            {

                //A[i]=lArr[m]<rArr[n]?lArr[m++]:rArr[n++];

 

                if(lArr[m]<rArr[n])

                {

                    A[i]=lArr[m];

                    m++;

                }

                else

                {

                    A[i]=rArr[n];

                    n++;

                }

            }

            else

            {

                if(m<nl)

                {

                    A[i]=lArr[m];

                    m++;

                }

                else

                {

                    A[i]=rArr[n];

                    n++;

                }

            }

        }

 

    }

 

    public void mergerSort(int []A,int p,int r)

    {   if(p == r){ 

        return; 

    }else

    {

        int q=(r+p)/2;

 

        mergerSort(A,p,q);

        mergerSort(A,q+1,r);

        merge(A,p,q,r);

    }

 

    }

    public static void main(String[] args) {

        // TODO Auto-generated method stub

        int a[]={1,3,2,5,6,4,8,7,9,11,10};

        for(int i=0;i<a.length;i++)

        {

            System.out.print(a[i]);

        }

        System.out.println();

        int r=a.length-1;

        System.out.println("长度"+r);

 

        MergeSort MS=new MergeSort();

        MS.mergerSort(a,0,r);

 

        for(int i=0;i<a.length;i++)

        {

            System.out.print(a[i]+"    ");

        }

        System.out.println();

    }

 

}