C++ 判断点是否在圆的内部

点到圆心的距离公式也就是两点间距离公式：

将类和main文件都写在一个文件中

#include <iostream>

using namespace std;

//点类
class Point{
  public:
    //设置一个点的坐标
    void setXY(int x, int y){
      m_x = x;
      m_y = y;
    }
  
    int getX(){
      return m_x;
    }
  
    int getY(){
      return m_y;
    }
  
  private:
    int m_x;  // 点的x轴坐标 
    int m_y;  // 点的y轴坐标 
};

//圆 类
class Circle{
  public:
    //设置坐标
    void setXY(int x, int y){
      m_x = x;
      m_y = y;
    }
  
    //设置半径
    void setR(int r){
      m_r = r;
    }
  
    //如果true 代表点在圆的内部
    bool judgePoint(Point& p){
      int d = (p.getX() - m_x) * (p.getX() - m_x) + (p.getY() - m_y) * (p.getY() - m_y);
  
      if (d > m_r * m_r) {
        return false;
      } else {
        return true;
      }
    }
  
  private:
    int m_x;  // 圆心的 x轴坐标 
    int m_y;  // 圆心的 y轴坐标 
    int m_r; // 圆的半径 
};

int main(void){
  Circle *circle = new Circle(); 
  Point *point = new Point();


  circle -> setXY(2, 2);
  circle -> setR(4);
  
  point -> setXY(5, 4);

  if (circle -> judgePoint(*point) == true) {
    cout << "点在圆的内部" << endl;
  } else {
    cout << "点在圆的外部" << endl;
  }
  
  delete circle;
  delete point;
}

---

将类和main分开成多个文件：

Circle.h文件

#pragma once
#include "Point.h"

//圆 类
class Circle{
  public:
    //设置坐标
    void setXY(int x, int y);
  
    //设置半径
    void setR(int r);
  
  
    //如果true 代表点在圆的内部
    bool judgePoint(Point& p);
  
  private:
    int m_x;
    int m_y;
    int m_r;
};

Point.h文件

#pragma once

class Point{
public:
  //设置一个点的坐标
  void setXY(int x, int y);

  int getX();

  int getY();


private:
  int m_x;
  int m_y;
};

Circle.cpp文件

#include "Circle.h"

void Circle::setXY(int x, int y)
{
  m_x = x;
  m_y = y;
}


//设置半径
void Circle::setR(int r)
{
  m_r = r;
}

//如果true 代表点在圆的内部
bool Circle::judgePoint(Point& p)
{
  int dd = (p.getX() - m_x) * (p.getX() - m_x) + (p.getY() - m_y) * (p.getY() - m_y);

  if (dd > m_r * m_r) {
    return false;
  }
  else {
    return true;
  }
}

Point.cpp文件

#include "Point.h"


//设置一个点的坐标
void Point::setXY(int x, int y){
  m_x = x;
  m_y = y;
}

int Point::getX(){
  return m_x;
}

int Point::getY(){
  return m_y;
}

main.cpp文件

#include <iostream>
#include "Circle.h"
#include "Point.h"

using namespace std;

int main(){
  Circle* circle = new Circle();
  Point* point = new Point();


  circle->setXY(2, 2);
  circle->setR(4);

  point->setXY(5, 4);

  if (circle->judgePoint(*point) == true) {
    cout << "点在圆的内部" << endl;
  }
  else {
    cout << "点在圆的外部" << endl;
  }

  delete circle;
  delete point;
}