用c++写一个基于tsp文件最短路径生成图片的代码

以下是一个基于TSP文件最短路径生成图片的C++代码示例，使用了STL库中的vector、pair和algorithm模块：

#include <iostream>
#include <fstream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <string>

using namespace std;

typedef pair<double, double> Point;
typedef vector<Point> Path;

double distance(Point p1, Point p2){
    double dx = p1.first - p2.first;
    double dy = p1.second - p2.second;
    return sqrt(dx*dx + dy*dy);
}

Path read_tsp_file(string filename){
    Path path;
    ifstream file(filename);
    string line;
    bool found = false;
    while (getline(file, line)){
        if (found){
            int id;
            double x, y;
            sscanf(line.c_str(), "%d %lf %lf", &id, &x, &y);
            path.push_back(make_pair(x, y));
        }
        else if (line == "NODE_COORD_SECTION"){
            found = true;
        }
    }
    return path;
}

int main(int argc, char *argv[]){
    if (argc < 2){
        cerr << "Usage: " << argv[0] << " <tsp_file>" << endl;
        return 1;
    }

    Path path = read_tsp_file(argv[1]);

    vector<int> order(path.size());
    for (int i = 0; i < path.size(); i++){
        order[i] = i;
    }

    double best_distance = -1;
    Path best_path;

    do {
        double distance = 0;
        for (int i = 0; i < order.size() - 1; i++){
            distance += ::distance(path[order[i]], path[order[i+1]]);
        }

        if (best_distance < 0 || distance < best_distance){
            best_distance = distance;
            best_path.clear();
            for (int i = 0; i < order.size(); i++){
                best_path.push_back(path[order[i]]);
            }
        }
    } while (next_permutation(order.begin(), order.end()));

    ofstream fout("output.ppm");
    fout << "P3" << endl;
    fout << path.size() << " " << path.size() << endl;
    fout << "255" << endl;

    for (int i = 0; i < path.size(); i++){
        for (int j = 0; j < path.size(); j++){
            if (i == j){
                fout << "255 255 255 ";
            }
            else {
                int r = (int)(255 * ::distance(path[i], path[j]) / best_distance);
                fout << r << " 0 0 ";
            }
        }
        fout << endl;
    }

    fout.close();

    return 0;
}

该代码从TSP文件中读取点的坐标，并使用暴力枚举算法计算最短路径。然后，它将生成一个PPM格式的图像文件，其中每个像素表示两个点之间的距离。这个像素的颜色表示两个点之间的距离与最短路径距离之比。白色像素表示同一点，黑色像素表示最远距离的点对。