C++ 使用坐标 xy
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Working with coordinates x y
提问by Asm
I need to read from a file coordinates of points. The file looks like this:
我需要从点的文件坐标中读取。该文件如下所示：
x0 y0
x0 y0
x1 y1
x1 y1
....
....
Then find center and diameter of the smallest enclosing circle. But I stucked in the beginning. I don't know how to hold coordinates and decided to choose array of structures. I've read coordinates into structure. I'm going to make 4 conditions:
然后找到最小封闭圆的中心和直径。但我一开始就卡住了。我不知道如何保持坐标并决定选择结构数组。我已将坐标读入结构中。我要提出4个条件：
1 - There is one point and you can't find the smallest enclosing circle.
1 - 有一点，你找不到最小的封闭圆。
2 - There are 2 points. Now the task is to find distance between them and its center.
2 - 有 2 分。现在的任务是找到它们与其中心之间的距离。
3 - There are 3 points.
3 - 有 3 分。
4 - More than 3 points. Use of special algorithm
4 - 超过 3 分。特殊算法的使用
I tried to use vector. I don't know how to use my points (elements of vector) later in functions etc.
我尝试使用矢量。我不知道以后如何在函数等中使用我的点（向量元素）。
#include "stdafx.h"
#include <stdio.h>
#include <fstream>
#include <iostream>
#include <vector>
using namespace std;
// Distance
float distance(){
return sqrt((point[0].x * point[1].x) + (point[0].y * point[1].y));
}
struct Points
{
float x, y;
};
int _tmain(int argc, _TCHAR* argv[])
{
vector<Points> point;
Points tmp;
ifstream fin("Points.txt");
if (!fin.is_open())
cout << "Cannot open the file \n";
else{
while (fin >> tmp.x >> tmp.y){
point.push_back(tmp);
cout << tmp.x << tmp.y << endl;
}
fin.close();
}
return 0;
}
回答by David K
I would name the struct something like Pointrather than Points,
since a single instance of the struct holds only one pair of x,y coordinates.
我会将结构命名为类似Point而不是Points，因为该结构的单个实例仅包含一对 x,y 坐标。
Then a suitable distance function might be something like
那么一个合适的距离函数可能是这样的
float distance(const Point& point1, const Point& point2)
{
return sqrt((point1.x * point2.x) + (point1.y * point2.y));
}
You can get the distance between any two points in your input set like this:
您可以像这样获得输入集中任意两点之间的距离：
distance(point[i], point[j])
You might also want to measure the distances from your input points to a point that is not in the set, such as a point where you think the center of the circle might be. For example,
您可能还想测量从输入点到不在集合中的点的距离，例如您认为圆心可能所在的点。例如，
distance(point[i], candidate_center_of_circle)
If it were my code, I would likely make Pointa class and give it a
member function for distance so that I could write something like
如果是我的代码，我可能会创建Point一个类并为其提供一个距离的成员函数，以便我可以编写类似
candidate_center_of_circle.distanceTo(point[i])
By the way, I mightname the variable pointsrather than pointbecause it is a vector that holds multiple instances of Point.
If you intend to write things like point[i]a lot you might not like
points[i], but if you are mostly going to make STL iterators over the vector
then you would have something like this:
顺便说一句，我可能会命名变量，points而不是point因为它是一个包含Point. 如果你打算写point[i]很多你可能不喜欢的东西
points[i]，但如果你主要是要在向量上制作 STL 迭代器，那么你会有这样的东西：
for (std::vector<Point>::const_iterator it = points.begin(); it != points.end(); ++it)
