在visual c++中分别实现直线段DDA算法、中点算法、Bresenham算法，要求： （1）三个算法写在一个程序中； （2）三个算法分别输入不同的起始点和终止点；

在Visual C++中实现直线段的三种绘制算法——DDA（Double Dithering Algorithm）、中点法(Midpoint Algorithm) 和 Bresenham算法，你可以创建一个包含三个函数的程序，每个函数处理一种算法。这里是一个简单的例子，假设我们已经有了`Point`结构体表示二维坐标，并有`drawLine()`函数作为公共接口，接收起点和终点。

#include <iostream>
using namespace std;

struct Point {
    int x;
    int y;
};

// 双线性插值算法 (DDA)
void drawLine_DDA(Point start, Point end) {
    double dx = end.x - start.x;
    double dy = end.y - start.y;
    int steep = abs(dy) > abs(dx);

    if (steep) {
        swap(start.x, start.y);
        swap(end.x, end.y);
    }

    double err = dx / 2.0; // 初始化误差
    for (int x = start.x; x <= end.x; ++x) {
        if (steep) {
            cout << start.y + floor(err) << " ";
            start.y += floor(dy);
        } else {
            cout << start.x << " ";
            start.x += 1;
        }
        err -= abs(dy);
        if (err < 0) {
            err += dx;
        }
    }
    cout << endl;
}

// 中点法
void drawLine_Midpoint(Point start, Point end) {
    if (start.x == end.x) { // 平行于y轴
        for (int y = start.y; y <= end.y; ++y) {
            cout << start.x << " ";
        }
    } else if (start.y == end.y) { // 平行于x轴
        for (int x = start.x; x <= end.x; ++x) {
            cout << x << " ";
        }
    } else {
        int dx = end.x - start.x;
        int dy = end.y - start.y;
        int error = 2 * dy - dx;
        while (start.x != end.x) {
            cout << start.x << " ";
            start.x++;
            if (error >= 0) {
                start.y++;
                error += 2 * dx;
            } else {
                error -= 2 * dy;
            }
        }
        cout << start.x << " "; // 输出终点
    }
    cout << endl;
}

// Bresenham算法
void drawLine_Bresenham(Point start, Point end) {
    int dx = abs(end.x - start.x);
    int dy = abs(end.y - start.y);
    bool swapped = false;
    if (start.x > end.x) {
        swap(start.x, end.x);
        swapped = true;
    }
    if (start.y > end.y) {
        swap(start.y, end.y);
    }
    int error = dx - dy;
    for (int x = start.x; x <= end.x; ++x) {
        if (!swapped) {
            cout << x << " ";
        } else {
            cout << start.y << " ";
        }
        error += 2 * dy;
        if (error >= dx) {
            error -= 2 * dx;
            start.y++;
        }
    }
    cout << endl;
}

int main() {
    Point start, end;
    cout << "请输入起始点(x,y): ";
    cin >> start.x >> start.y;
    cout << "请输入终止点(x,y): ";
    cin >> end.x >> end.y;

    cout << "DDA算法: ";
    drawLine_DDA(start, end);

    cout << "中点算法: ";
    drawLine_Midpoint(start, end);

    cout << "Bresenham算法: ";
    drawLine_Bresenham(start, end);

    return 0;
}