#ifndef __CRICLE_H__ #define __CRICLE_H__ #include "point.h" class Circle { public:   //創建圓   void init(int r, int x, int y);   //判斷點是否在 當前圓 內   bool inCircle(Point &p); private:   Point _c;   int _r; };  #endif// __CRICLE_H__ 

#ifndef __POINT_H__ #define __POINT_H__  class Point { public:   //創建點   void init(int x, int y);   //測一個點和當前點的距離的平方   int distance(Point &p); private:   int _x;   int _y; };  #endif//__POINT_H__ 

#include "circle.h"  void Circle::init(int r, int x, int y) {   _r = r;   _c.init(x, y); }  bool Circle::inCircle(Point &p) {   //計算點p和 當前圓圓心c 的距離   int dis = p.distance(_c);    //和半徑比較   if (dis <= _r*_r)     return true;   else     return false; } 

#include "point.h"  void Point::init(int x, int y) {   _x = x;   _y = y; }  int Point::distance(Point &p) {   int dis = (_x-p._x)*(_x-p._x)     + (_y-p._y)*(_y-p._y);    return dis; } 

#include <iostream> #include "circle.h" #include "point.h" using namespace std;  int main() {   //一個點   Point p;   p.init(1,2);    Circle c;   c.init(3, 0, 0);    if (c.inCircle(p))     cout << "在圓內" << endl;   else     cout << "在圓外" << endl;    return 0; }