归并排序

package my0410;

public class MergeSort {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
    
        int a[]={9,8,7,6,5,4,3,2,1};
        int[] aux = (int[])a.clone(); 
        
        mergeSort(aux, a,0,a.length);  
        for(int i=0;i<a.length;i++){  
            System.out.println(a[i]);  
        } 

    }
    //low到high-1，不包括high
    public static void mergeSort(int []data,int []temp,int low,int high){
        if(low==high-1){//注意边界条件
            return;
        }
        int mid=(low+high)/2;    
        mergeSort(temp,data,low,mid);
        mergeSort(temp,data,mid,high);
        int i,p=low,q=mid;
        for(i=low;p<mid&&q<high;i++){
            if(data[p]<data[q]){
                temp[i]=data[p++];
            }else{
                temp[i]=data[q++];
            }
        }
        while(p<mid&&i<high){
            temp[i++]=data[p++];
            
        }
        while(q<high&&i<high){
            temp[i++]=data[q++];
        }
        
    }

}