1．代码实现。
#include
using namespace std;
class CCircle; //①
class CPoint
{
public:
unsigned x;
unsigned y;
bool IsInCircle(CCircle *Circle); //判断点是否在圆内-②
};
class CCircle
{
public:
unsigned Radius;
CPoint Center;
};
bool CPoint::IsInCircle(CCircle Circle)
{
return (((x-Circle->Center.x)(x-Circle->Center.x)
+(y-Circle->Center.y)(y-Circle->Center.y))<=Circle->RadiusCircle->Radius);
}
int main()
{
//补充代码
}
问题1：补充main()代码，实现测试（1）点1（3，4），圆半径=5，圆心（0，0）是否在圆内；测试（2） 点2（5，4）,圆半径=3，圆心（2，1）是否在圆内。
问题2：①代码去掉，代码能否正确执行，不能给出原因。
问题3：② IsInCircle(CCircle *Circle)实现类内定义及实现，代码能否正确执行，如果不能，请给出原因。
代码补充如下：
#include <iostream>
using namespace std;
class CCircle; //①
class CPoint
{
public:
unsigned x;
unsigned y;
bool IsInCircle(CCircle* Circle); //判断点是否在圆内-②
};
class CCircle
{
public:
unsigned Radius;
CPoint Center;
};
bool CPoint::IsInCircle(CCircle* Circle)
{
return (((x - Circle->Center.x)*(x - Circle->Center.x)
+ (y - Circle->Center.y)*(y - Circle->Center.y)) <= Circle->Radius*Circle->Radius);
}
int main()
{
//补充代码
CCircle c1;
c1.Radius = 5;
c1.Center.x = 0;
c1.Center.y = 0;
CPoint p1;
p1.x = 3;
p1.y = 4;
if (p1.IsInCircle(&c1))
cout << "在圆内" << endl;
else
cout << "不在圆内" << endl;
CCircle c2;
c2.Center.x = 2;
c2.Center.y = 1;
c2.Radius = 3;
CPoint p2;
p2.x = 5;
p2.y = 4;
if (p2.IsInCircle(&c2))
cout << "在圆内" << endl;
else
cout << "不在圆内" << endl;
return 0;
}
问题2：①代码去掉，代码能否正确执行，不能给出原因。
答：去掉后不能执行，编译报错，因为CCircle类的声明在CPoint类的后面，去掉①代码后，CPoint类中使用CCircle类时无法识别该类型。
问题3：② IsInCircle(CCircle *Circle)实现类内定义及实现，代码能否正确执行，如果不能，请给出原因。
答：不能。在类内实现时，CCircle类还没有具体实现，在IsInCircle函数中无法识别CCircle类的成员变量。
圆心肯定在园内啊，是某个点是否在园内吧
#include <iostream>
using namespace std;
class CCircle;
class CPoint
{
public:
unsigned x;
unsigned y;
bool IsInCircle(CCircle *Circle);
};
class CCircle
{
public:
unsigned Radius;
CPoint Center;
};
bool CPoint::IsInCircle(CCircle *Circle)
{
return (((x-Circle->Center.x)*(x-Circle->Center.x)+(y-Circle->Center.y)*(y-Circle->Center.y))<=Circle->Radius*Circle->Radius);
}
int main()
{
CPoint pt1;
pt1.x = 3;
pt1.y = 4;
CCircle c1;
c1.Radius = 5;
c1.Center.x = 0;
c1.Center.y = 0;
if(pt1.IsInCircle(&c1))
cout<<"点(3,4)在圆内"<<endl;
else
cout<<"点(3,4)不在圆内"<<endl;
//
CPoint pt2;
pt2.x = 5;
pt2.y = 4;
CCircle c2;
c2.Radius = 3;
c2.Center.x = 2;
c2.Center.y = 1;
if(pt2.IsInCircle(&c2))
cout<<"点(5,4)在圆内"<<endl;
else
cout<<"点(5,4)不在圆内"<<endl;
return 0;
}
#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;
}
主函数
#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;
}