C++判断一个点是否在圆内的方法

#ifndef __CRICLE_H__ 
#define __CRICLE_H__ 
#include "point.h" 
class Circle 
{ 
public: 
  //创建圆 
  void init(int r, int x, int y); 
  //判断点是否在 当前圆 内 
  bool inCircle(Point &p); 
private: 
  Point _c; 
  int _r; 
}; 
 
#endif// __CRICLE_H__ 

#ifndef __POINT_H__ 
#define __POINT_H__ 
 
class Point 
{ 
public: 
  //创建点 
  void init(int x, int y); 
  //测一个点和当前点的距离的平方 
  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) 
{ 
  //计算点p和 当前圆圆心c 的距离 
  int dis = p.distance(_c); 
 
  //和半径比较 
  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() 
{ 
  //一个点 
  Point p; 
  p.init(1,2); 
 
  Circle c; 
  c.init(3, 0, 0); 
 
  if (c.inCircle(p)) 
    cout << "在圆内" << endl; 
  else 
    cout << "在圆外" << endl; 
 
  return 0; 
}