Code Fights - circleOfNumbers

README.md

Consider integer numbers from 0 to n - 1 written down along the circle in such a way that the distance between any two neighbouring numbers is equal (note that 0 and n - 1 are neighbouring, too).

Given n and firstNumber, find the number which is written in the radially opposite position to firstNumber.

Example

For n = 10 and firstNumber = 2, the output should be
circleOfNumbers(n, firstNumber) = 7.

Input/Output

• [time limit] 4000ms (py3)

• [input] integer n

  A positive even integer.

  Guaranteed constraints:

  4 ≤ n ≤ 20.
  

• [input] integer firstNumber

  Guaranteed constraints:

   0 ≤ firstNumber ≤ n - 1.
  

• [output] integer

circle_of_numbers.py

def circle_of_numbers(n, first_num):
    return int((n / 2 + first_num) % n)

test_circle_of_numbers.py

import unittest
from circle_of_numbers import circle_of_numbers


class MyTestCase(unittest.TestCase):
    def test_1(self):
        n = 10
        first_number = 2
        solution = 7
        result = circle_of_numbers(n, first_number)
        self.assertEqual(result, solution)

    def test_2(self):
        n = 10
        first_number = 7
        solution = 2
        result = circle_of_numbers(n, first_number)
        self.assertEqual(result, solution)

    def test_3(self):
        n = 4
        first_number = 1
        solution = 3
        result = circle_of_numbers(n, first_number)
        self.assertEqual(result, solution)

    def test_4(self):
        n = 6
        first_number = 3
        solution = 0
        result = circle_of_numbers(n, first_number)
        self.assertEqual(result, solution)


if __name__ == '__main__':
    unittest.main()