Practice>Python>Classes>Class 2 - Find the Torsional Angle

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Class 2 - Find the Torsional Angle

Problem link : https://www.hackerrank.com/challenges/class-2-find-the-torsional-angle/problem

Difficulty : Easy, (It should be Medium at least)

Tip

• Using class in python is not difficult
• However, you should know vector's cross product, and implement it.
• If not, please refer http://tutorial.math.lamar.edu/Classes/CalcII/CrossProduct.aspx
• method cross() should return instance of Points class

Solution

import math class Points(object): def __init__(self, x, y, z): self.x = x self.y = y self.z = z def __sub__(self, pt): return Points(self.x - pt.x, self.y - pt.y, self.z - pt.z) def dot(self, pt): return (self.x*pt.x) + (self.y*pt.y) + (self.z*pt.z) def cross(self, pt): return Points(self.y*pt.z-self.z*pt.y, self.z*pt.x-self.x*pt.z, self.x*pt.y-self.y*pt.x) def absolute(self): return pow((self.x ** 2 + self.y ** 2 + self.z ** 2), 0.5) if __name__ == '__main__': points = list() for i in range(4): a = list(map(float, input().split())) points.append(a) a, b, c, d = Points(*points[0]), Points(*points[1]), Points(*points[2]), Points(*points[3]) x = (b - a).cross(c - b) y = (c - b).cross(d - c) angle = math.acos(x.dot(y) / (x.absolute() * y.absolute())) print("%.2f" % math.degrees(angle))