归并排序

import java.util.Arrays;


public class MergeSort {

    private static void merge(int[] a,int low,int mid,int high){
        int[] temp=new int[high-low+1];
        int i=low;//左指针
        int j=mid+1;//右指针
        int k=0;
        //把较小的数移到新数组中
        while(i<=mid&&j<=high){
            if(a[i]<a[j]){
                temp[k++]=a[i++];
            }else{
                temp[k++]=a[j++];
            }
        }
        //把左边剩余的数移入数组
        while(i<=mid){
            temp[k++]=a[i++];
        }
        //把右边剩余的数移入数组
        while(j<=high){
            temp[k++]=a[j++];
        }
        //把数据从临时数组复制到原来的数组
        for(int k2=0;k2<temp.length;k2++){
            a[k2+low]=temp[k2];
        }
    }
    /*
     * 每次归并的有序集合长度
     */
    public static int[] mergeSort(int[] a,int low,int high){
        int mid=(low+high)/2;
        if(low<high){
            //左边
            mergeSort(a,low,mid);
            //右边
            mergeSort(a,mid+1,high);
            //左右归并
            merge(a, low, mid, high);
        }
        return a;
    }
    public static void main(String[] args) {
        int []a={2,7,8,3,1,6,9,0,5,4};
        mergeSort(a, 0, a.length-1);
        System.out.println(Arrays.toString(a));
    }

}