Question

I have two locations, My player location (2D) and I’m looping over a vector of entitys each with a location (2D), I would like my function to return the closest distance to my location, But I don’t know how to do it because I got stuck, in c# I could just use linq, But i’m learning c++ My function looks like this:

const Entity GetNearestEntity()
{
    for (Entity i : fb.Entities)
    {
        double xDiff = (double)abs(fb.PlayerLocation.X - i.X);
        double yDiff = (double)abs(fb.PlayerLocation.Y - i.Y);

        //Stuck here.. 
        //How can i get the closest object out of my vector<Entity> collection?
    }
}

help appreciated!

Answer 1

This may be easier to do by keeping track of the index of the closest element to you, which would be easier in a ‘for’ loop like:

Entity GetNearestEntity()
{
    int closestEnt = 0;
    double smallestDist = -1.0;

    for (int i = 0; i < Entities.length(); i++) 
    {
        double xDiff = (double)abs(fb.PlayerLocation.X - Entities[i].X);
        double yDiff = (double)abs(fb.PlayerLocation.Y - Entities[i].Y);
        double totalDist = sqrt(pow(xDiff, 2) + pow(yDiff, 2));

        if ((totalDist < smallestDist) || (smallestDist == -1.0))
        {
            closestEnt = i;
            smallestDist = totalDist;
        }
    }

    return Entities[closestEnt];
}

This may not compile off the bat, it’s been a while since I’ve played with C++, and I’m blanking on whether that’s the right way to do square roots and powers. However, it has the nice benefit of only keeping track of a double and an int, instead of an object.