如何从列表中删除多个元素

Question

This is the list...

 List<Location> locations = new List<Location>();
 locations.Add(new Location("Narayana International", 28.6075582, 77.04700729999999));
 locations.Add(new Location("Digital zone", 28.8610328484855, 77.0951520020164));
 locations.Add(new Location("Vijay computers", 28.841364952771706, 77.09076910484801));
 locations.Add(new Location("Codac Info", 29.967759964202948, 76.88406425590289));
 locations.Add(new Location("Balaji computers", 30.6920753011206, 76.80162611916126));
 locations.Add(new Location("Aadi online exam solutions", 30.393033405609803, 76.79088732285474));

Calculate distance with current location then find nearest location and print it on console then remove that location,again find nearest location and print on console then remove the location this itration continue till 4 elements are remove..

Now, This is my code which i have tried but how to remove multiple elements..

List<Location> locations = new List<Location>();
   locations.Add(new Location("Narayana International", 28.6075582, 77.04700729999999));
   locations.Add(new Location("Digital zone", 28.8610328484855, 77.0951520020164));
   locations.Add(new Location("Vijay computers", 28.841364952771706, 77.09076910484801));
   locations.Add(new Location("Codac Info", 29.967759964202948, 76.88406425590289));
   locations.Add(new Location("Balaji computers", 30.6920753011206, 76.80162611916126));
   locations.Add(new Location("Aadi online exam solutions", 30.393033405609803, 76.79088732285474));
  
   double searchLat = 19;
   double searchLong = 74;

   Dictionary<double, List<Location>> distances = new Dictionary<double, List<Location>>();

   locations.ForEach(location =>
   {
       double distance = Program.GetDistance(location.Latitude, location.Longitude, searchLat, searchLong);
       if (distances.ContainsKey(distance))
       {
           distances[distance].Add(location);
       }
       else
       {
           distances.Add(distance, new List<Location>() { location });
       }

   });
   Console.WriteLine("Locations Are:" + locations.Count);
   Console.WriteLine(locations);
   Console.WriteLine("This is the nearest location to me:");

 
   var abc = locations.OrderBy(x => x.Place).ToList();
   double closestDistanceFromSearch = distances.Keys.OrderBy(k => k).First();
   Console.WriteLine(distances[distances.Keys.OrderBy(k => k).First()].Select(x => x.Place).ToList());

  

 locations.RemoveAt(0); // remove object at position 1, in this case 
      Console.WriteLine("Elements are remove:" );
     foreach (var a in locations)
          Console.WriteLine(a.ToString());
  Console.WriteLine("Now the count is : "+ locations.Count  );
           Console.ReadLine();

      


public static double GetDistance(double latitude, double longitude, double otherLatitude, double otherLongitude) {
    var d1 = latitude * (Math.PI / 180.0);
    var num1 = longitude * (Math.PI / 180.0);
    var d2 = otherLatitude * (Math.PI / 180.0);
    var num2 = otherLongitude * (Math.PI / 180.0) - num1;
    var d3 = Math.Pow(Math.Sin((d2 - d1) / 2.0), 2.0) + Math.Cos(d1) * Math.Cos(d2) * Math.Pow(Math.Sin(num2 / 2.0), 2.0);
   // var d3 = Math.Sqrt((Math.Pow(d1  - d2 , 2) + Math.Pow(num1 - num2, 2)));
   Console.WriteLine(d3);

  return 6376500.0 * (2.0 * Math.Atan2(Math.Sqrt(d3), Math.Sqrt(1.0 - d3)));

   
}

Answer 1

I would assume the intent is to use a simple loop. This can be easily done with MinBy if you are using a recent version of .net:

for(int i=0; i < 4; i++){
    var closest = locations.MinBy(l => GetDistance(l.Latitude, l.Longitude, searchLat, searchLong);
    Console.WriteLine(closest.Name);
    locations.Remove(closest);
}

A better solution would be to calculate all the distances to all the locations and do a (partial) sort to get the 4 closest items. Allowing you to get the same result without the need to change the original collection. But that seem to go against the intent of the assignment.