分治思想--小测试(归并排序后续)

package cn.it;

import java.util.Arrays;
// 利用分治思想 实现  归并排序
public class Fz {
    public static void main(String[] args) {
        int a[]={1,2,3,4,5,6,8,7,3,4,9,0};
        int temp[] = new int[a.length];
        sortdiv(a, 0, a.length-1, temp);
        System.out.println(Arrays.toString(a));
    }
    
    private static  void sortdiv(int[] a,int start,int end,int[] temp){
        if(start<end){
            //后序遍历 递归左子树 递归右子树 跟
            int mid=(start+end)/2;
            sortdiv(a, start, mid,temp);
            sortdiv(a, mid+1, end,temp);
            merge(a, start, end, mid,temp);
        }
    }
    
    private static void merge(int[] a,int start,int end,int mid,int[] temp){
        int i=start;
        int j=mid+1;
        int k=0;

        //将较少者存入临时空间
        while(i<=mid && j<=end){
            if(a[i]<a[j]){
                temp[k++]=a[i++];
            }else{
                temp[k++]=a[j++];
            }
        }
        
        //剩余的加入队尾
        while(i<=mid){
            temp[k++]=a[i++];
        }
        
        while(j<=end){
            temp[k++]=a[j++];
        }
        
        //将有序临时数组置换回实际存储的数组
        for(int l=0;l<k;l++){
            a[start+l]=temp[l];
        }
        
    }
}