#include <iostream.h>

int findx();

int n,x,mid,high,low;
int *A;

int main()
{
	int j;
	cout<<"請輸入元素個數n:";
	cin>>n;
	cout<<"請輸入數組A[]";
	A=new int;
	for (int i=0;i<n;i++) cin>>A[i];
	cout<<"請輸入需查找的元素x:";
	cin>>x; 
	low=1;
	high=n;
	j=findx()+1;
	if(j==0) cout<<"找不到！"<<endl;
    cout<<"找到x，它在數組中的第"<<j<<"個位置。"<<endl;

	return 0;
}

int findx()
{
	mid=(low+high)/2;
	if(x==A[mid]) return mid;
	else if(low>high) return -1;
	if(x>A[mid]) 
	{
		low=mid+1;
		return findx();
	}
	else if(x<A[mid])
	{
		high=mid-1;
        return findx();
	}
	else return findx();
}