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 point_to_line_distance(point, line):
    # 计算点到直线的距离
    x1, y1 = line.point_A.x, line.point_A.y
    x2, y2 = line.point_B.x, line.point_B.y
    x0, y0 = point.x, point.y
    
    # 直线方程 Ax + By + C = 0
    A = y2 - y1
    B = x1 - x2
    C = x2 * y1 - x1 * y2
    
    distance = abs(A * x0 + B * y0 + C) / math.sqrt(A**2 + B**2)
    return distance

def getDistance(circle, l):
    # 请在这里实现你的代码
    # 计算圆心到直线的距离
    d = point_to_line_distance(circle.O, l)
    
    # 计算交点之间的距离
    if d < circle.r:
        return 2 * math.sqrt(circle.r**2 - d**2)
    else:
        return 0














































































































































































































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()