C++:将元素从 unordered_set 复制到 vector

Question

背景:我正在为旅行商问题实现最近邻算法。我需要计算旅行的距离以及跟踪访问点的顺序。我定义了一个带有实例变量 x 和 y 的点类，以及一个用于计算两点之间距离的函数 calcDist。我首先将所有点存储在名为 points 的 std::unordered_set 中，创建一个名为 path 的空 std::vector 存储游览路径，并将起点分配给 startPoint，并将这些传递给我的 nearestNeighbor() 函数:

void nearestNeighbor(unordered_set<Point, PointHasher> points, vector<Point> &path, Point startPoint) {
  // Declare variables
  unordered_set<Point, PointHasher>::iterator it;
  Point currentLocation, possibleNeighbor, nearestNeighbor;
  double totalDist = 0;
  int pointsCount = path.capacity() - 1;

  // Set the starting location
  it = points.find(startPoint);
  currentLocation = *it;
  path[0] = currentLocation;
  points.erase(currentLocation);
  cout << "Start location: " << path[0].x << ", " << path[0].y << endl;

  // Create the path
  for (int i = 1; points.size() > 0; i++) {
    double minDist = -1;
    // Find the current location's nearest neighbor
    for (it = points.begin(); it != points.end(); it++) {
      possibleNeighbor = *it;
      int currentDist = currentLocation.calcDist(possibleNeighbor);
      if (minDist == -1 || currentDist < minDist) {
        minDist = currentDist;
        nearestNeighbor = possibleNeighbor;
      }
    }
    // Record nearest neighbor data and prepare for the next iteration
    currentLocation = nearestNeighbor;
    path[i] = currentLocation;
    points.erase(currentLocation);
    totalDist += minDist;
    cout << "Nearest neighbor: " << path[i].x << ", " << path[i].y << endl;
  }
  // Return to the starting location
  path[pointsCount] = startPoint;
  cout << "End location: " << startPoint.x << ", " << startPoint.y << endl;
  cout << "Path:" << endl;
  for (int i = 0; i < path.size(); i++) {
    cout << path[0].x << ", " << path[0].y << endl;
  }
  cout << "Total distance: " << totalDist << endl;
}

问题在于，一旦程序退出外层 for 循环，path 中的所有点都会以某种方式被覆盖。要明白我的意思，这里是输出:

Start location: 3, 4
Nearest neighbor: 6, 8
Nearest neighbor: 11, 7
Nearest neighbor: 50, 8
End location: 3, 4
Path:
3, 4
3, 4
3, 4
3, 4
3, 4
Total distance: 49
Press any key to continue . . .

我认为这要么是 vector 元素的指针/地址有问题，要么是范围问题，因为问题发生在退出 for 循环之后。我什至尝试在每次迭代后打印 path[1] 以查看它何时更改，但它在整个循环中都是正确的，并且只在最后的输出中发生变化。有什么想法吗？我很难过。如果您已经走到这一步，非常感谢您抽出宝贵时间。

Answer 1

你总是输出 path[0] man 的坐标

for (int i = 0; i < path.size(); i++) {
    cout << path[0].x << ", " << path[0].y << endl;
}