java - 如何从列表中获取最接近给定目标的 vector

Question

假设我在 Java 中创建了一个带有两个变量 x 和 y 的 Vector 类:

public class Vector {
    private int x;
    private int y;

    public Vector(int x, int y) {
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return this.x;  
    }

    public int getY(){
        return this.y;
    }
}

然后我创建了一个 ArrayList vector :

private List<Vector> vecs = new ArrayList<Vector>();

我在该列表中创建了:

8,9
10,5
83473834,938849584985
etc ...

现在我想获得最接近另一个 vector 的 vector 。示例:

private List<Vector> vecs = new ArrayList<Vector>();
private Vector vec = new Vector(1,1);

for(Vector vector:vecs) {
    //What do i put here??
}

那么我应该在 for 循环中放置什么才能使其从 vector 列表中选择最近的 vector ？

Answer 1

我将从向 Vector 类 distanceTo 添加一个方法开始，该方法计算从该 vector 到另一个 vector 的距离:

public double distanceTo(Vector vec) {
    double dx = x - vec.x;               //calculate the diffrence in x-coordinate
    double dy = y - vec.y;               //calculate the diffrence in y-coordinate
    return Math.sqrt(dx*dx + dy*dy);     //use the distance formula to find the difference
}

然后您可以编写以下方法，返回列表中最接近给定 vector 的 vector :

public static Vector closest(Vector target, List<Vector> list) {
    Vector closest = list.get(0);                                 //this variable will kep track of the closest vector we have found yet. We simply start with the first one

    for(int i = 1; i < list.size(); i++) {                        //loop over the list, skipping the first entry
        Vector curr = list.get(i);                                //get the current vector from the list
        if (target.distanceTo(curr) < target.distanceTo(closest))    //if the current vector is closer to target than the closest one yet
            closest = curr;                                       //keep the current vector as the new closest one
    }

    return closest;                                               //return the resulting vector
}

然后可以像这样使用此方法:

Vector target = new Vector(1, 2);

List<Vector> vecs = new ArrayList<Vector>();
vecs.add(new Vector(-2, 6));
vecs.add(new Vector(1, 3));
vecs.add(new Vector(4, 0));
vecs.add(new Vector(8, -1));

Vector closest = findClosest(target, vecs);

如您所见，我已尽力解释代码，但如有任何其他问题，请随时提出!

编辑另一种方法是:

 public double distanceTo(Vector vec1,Vector vec2) {
        double dx = vec2.x - vec1.x;               //calculate the diffrence in x-coordinate
        double dy = vec.y - vec1.y;               //calculate the diffrence in y-coordinate
        return Math.sqrt(dx*dx + dy*dy);     //use the distance formula to find the difference
    }

这是如果你不能把它放到 vector 类中