题解 | 点到直线距离

import java.util.Scanner;
// 参考：https://blog.nowcoder.net/n/ef1490ffaa244654b7f9b2f556bee498
public class Main {
    static class Point {
        double x, y;

        Point(double a, double b) {
            x = a;
            y = b;
        }
    }

    static class Line {
        Point pointA, pointB;

        Line(Point a, Point b) {
            pointA = a;
            pointB = b;
        }
    }

    static double distance(Point a, Point b) {
        return Math.sqrt(Math.pow(a.x - b.x, 2) + Math.pow(a.y - b.y, 2));
    }

    static double getDistance(Point P, Line L) {
        // TODO: 计算点P到直线L的距离
        double pa = distance(P,L.pointA);
        double ab = distance(L.pointA,L.pointB);
        double pb = distance(P,L.pointB);

        double cosA = (pa*pa+ab*ab-pb*pb)/(2*pa*ab);// 余弦定理
        double sinA = Math.sqrt(1-cosA*cosA);
        return pa*sinA;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        int sx = scanner.nextInt();
        int sy = scanner.nextInt();
        int tx = scanner.nextInt();
        int ty = scanner.nextInt();

        Point pointA = new Point(sx, sy);
        Point pointB = new Point(tx, ty);
        Point pointC = new Point(a, b);
        Line line = new Line(pointA, pointB);

        System.out.printf("%.2f", getDistance(pointC, line));
        scanner.close();
    }
}

蓝色线条的长度