#include"iostream"
#include"algorithm"
using namespace std;
class list{
private:
	int data[20];
	int length;
public:
	list()
	{
		cout << "元素個數為：" << endl ;
		cin >> length ;
		cout << "請輸入順序表元素" << endl ;
		for(int i=0;i<length;i++)
			cin >> data[i];
	}
	void listsort()
	{
		sort(data,data+length);
		for(int i=0;i<length;i++)
			cout << data[i] << "  ";
		cout << endl ;
	}
	void binsearch(int key,int a)
	{
		int half;
		half=a/2;
		if(data[half]==key&&half!=0)
			cout << "關鍵字的編號為: " << half+1 << endl ;
		else if(data[half]>key&&key>data[0])
		{
			cout << "順序表的中值比關鍵字大，繼續在0—" << half << "中查詢" << endl ;
			binsearch(key,half);
		}
		else if(data[half]<key&&key<data[length-1])
		{
			cout << "順序表的中值比關鍵字小，繼續在" << half << "-" << length << "中查詢" << endl ;
			binsearch(key,half+length);
		}
		else
			cout << "關鍵字不存在" << endl ;
	}
	int getlength()
	{
		return length;
	}
};

void main()
{
	int key;
	list a;
	a.listsort();
	cout << "請輸入關鍵字" << endl ;
	cin >> key ;
	a.binsearch(key,a.getlength());

}