一条线段如何向两边 扩大 c++代码

以下是一个简单的C++函数，可以将一条线段向两边扩大指定的距离：

#include <iostream>
#include <cmath>

using namespace std;

struct Point {
    double x, y;
};

struct Line {
    Point start, end;
};

// 计算两点之间的距离
double distance(Point p1, Point p2) {
    return sqrt(pow(p2.x - p1.x, 2) + pow(p2.y - p1.y, 2));
}

// 计算线段的斜率
double slope(Line line) {
    return (line.end.y - line.start.y) / (line.end.x - line.start.x);
}

// 计算线段的长度
double length(Line line) {
    return distance(line.start, line.end);
}

// 将线段向两边扩大指定的距离
void expand(Line& line, double distance) {
    double dx = (line.end.x - line.start.x) * distance / length(line);
    double dy = (line.end.y - line.start.y) * distance / length(line);

    Point left = {line.start.x - dy, line.start.y + dx};
    Point right = {line.end.x - dy, line.end.y + dx};

    line.start = left;
    line.end = right;
}

int main() {
    Line line = {{0, 0}, {3, 4}};
    double distance = 1;

    cout << "Original line: (" << line.start.x << "," << line.start.y << ") to (" << line.end.x << "," << line.end.y << ")" << endl;

    expand(line, distance);

    cout << "Expanded line: (" << line.start.x << "," << line.start.y << ") to (" << line.end.x << "," << line.end.y << ")" << endl;

    return 0;
}

这个函数采用结构体表示点和线段，使用欧几里得距离计算点之间的距离，使用勾股定理计算线段长度，并使用向量的方法将线段向两边扩大指定的距离。