#include<stdio.h>

int seek(int * pArr,int low,int high,int num);

void main()

{

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

int find,num;

printf("input a num to be found.\n");

scanf("%d",&num);

find = seek(Arr,0,9,num);

if (find == -1) printf("num=%d not found!\n",num);

else printf("num has been found!\nArr[%d] = %d\n",find,Arr[find]);

}

int seek (int *pArr,int low,int high,int num)

{//pArr 為陣列名，該陣列必須是排好序了（這是二分法的要求），這裡按從小到大排序

int mid;

mid = (low+high)/2;

if ((low>=high)&&(pArr[mid]!=num))

return -1;

else

{

if (pArr[mid]==num)

return mid;

else if (pArr[mid]>num)

high = mid+1;//中間數字比要查的數還大，說明可能在中間段以前

else

low = mid-1;//同上，可能在中間段以後

return seek(pArr,low,high,num); //遞迴

}

}