题解 | 直线与圆交点间距

import math
class Point:
    def __init__(self, A, B):
        self.x = A
        self.y = B

class Line:
    def __init__(self, A, B):
        self.point_A = A
        self.point_B = B

class Circle:
    def __init__(self, A, B):
        self.O = A
        self.r = B

def getDistance(circle, l):
    # 请在这里实现你的代码
    pass
    #先求直线L点斜式 k , C
    #先求圆心到直线的距离
    if l.point_A.x == l.point_B.x:
        h = abs(circle.O.x - l.point_A.x )
    else :
        x_a,y_a, x_b , y_b = l.point_A.x, l.point_A.y , l.point_B.x , l.point_B.y
        k = (y_b - y_a) / (x_b - x_a)
        c = y_a - k * x_a
        h = abs(k * circle.O.x - circle.O.y + c) / math.sqrt(k**2 +1)

    #判断直线是否与圆相交，再求弦长     
    if h >= circle.r:
        d = 0.0
    else:
        d =2 *  math.sqrt(circle.r **2 - h ** 2)
    return d



def main():
    ox, oy, r = map(float, input().split())
    x1, y1, x2, y2 = map(float, input().split())
    
    center = Point(ox, oy)
    circle = Circle(center, int(r))
    
    p1 = Point(x1, y1)
    p2 = Point(x2, y2)
    l = Line(p1, p2)
    
    result = getDistance(circle, l)
    print("{:.6f}".format(result))

if __name__ == "__main__":
    main()