#include <stdio.h>    
  int bin_search(int key[],int low, int high,int k)   
  {   
    int mid;   
    if(low>high)
    {
       return -1;   
    }
    else 
     {   
         mid = (low+high) / 2;   
         if(key[mid]==k)   
             return mid;   
         if(k>key[mid])   
             return bin_search(key,mid+1,high,k);        /*在序列的后半部分查找*/   
         else   
             return bin_search(key,low,mid-1,k);            /*在序列的前半部分查找*/   
      }   
 }   

 int main()   
 {   
     int n , i , addr;   
     int A[10] = {2,3,5,7,8,10,12,15,19,21};   
      printf("The contents of the Array A[10] are/n");   
      for(i=0;i<10;i++) 
         printf("%d ",A[i]);                                /*顯示數組A中的內容*/   
      printf("/nPlease input a interger for search/n");   
      scanf("%d",&n);                                /*輸入待查找的元素*/   
      addr = bin_search(A,0,9,n);   
      if(-1 != addr)    /*查找成功*/   
 {
         printf("%d is at the %dth unit is array A/n ",n,addr);   
 }
      else
 {
  printf("There is no %d in array A/n",n);            /*查找失敗*/   
 }
  getchar();   
  return 0;   
  }