點到圓心的距離公式也就是兩點間距離公式：

將類和main文件都寫在一個文件中

#include <iostream>using namespace std;//點類 class Point{public://設置一個點的坐標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; // 點的x軸坐標 int m_y; // 點的y軸坐標 };//圓 類 class Circle{public://設置坐標void setXY(int x, int y){m_x = x;m_y = y;}//設置半徑void setR(int r){m_r = r;}//如果true 代表點在圓的內部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; // 圓心的 x軸坐標 int m_y; // 圓心的 y軸坐標 int m_r; // 圓的半徑 };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 << "點在圓的內部" << endl;} else {cout << "點在圓的外部" << endl;}delete circle;delete point; }

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將類和main分開成多個文件：

Circle.h文件

#pragma once #include "Point.h"//圓 類 class Circle{public://設置坐標void setXY(int x, int y);//設置半徑void setR(int r);//如果true 代表點在圓的內部bool judgePoint(Point& p);private:int m_x;int m_y;int m_r; };

Point.h文件

#pragma onceclass Point{ public://設置一個點的坐標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; }//設置半徑 void Circle::setR(int r) {m_r = r; }//如果true 代表點在圓的內部 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"//設置一個點的坐標 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 << "點在圓的內部" << endl;}else {cout << "點在圓的外部" << endl;}delete circle;delete point; }

總結

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