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267b5eff40
* Added doctest and more explanation about Dijkstra execution. * tests were not passing with python2 due to missing __init__.py file at number_theory folder * Removed the dot at the beginning of the imported modules names because 'python3 -m doctest -v data_structures/hashing/*.py' and 'python3 -m doctest -v data_structures/stacks/*.py' were failing not finding hash_table.py and stack.py modules. * Moved global code to main scope and added doctest for project euler problems 1 to 14. * Added test case for negative input. * Changed N variable to do not use end of line scape because in case there is a space after it the script will break making it much more error prone. * Added problems description and doctests to the ones that were missing. Limited line length to 79 and executed python black over all scripts. * Changed the way files are loaded to support pytest call. * Added __init__.py to problems to make them modules and allow pytest execution. * Added project_euler folder to test units execution * Changed 'os.path.split(os.path.realpath(__file__))' to 'os.path.dirname()'
62 lines
1.0 KiB
Python
62 lines
1.0 KiB
Python
# -*- coding: utf-8 -*-
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"""
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By listing the first six prime numbers:
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2, 3, 5, 7, 11, and 13
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We can see that the 6th prime is 13. What is the Nth prime number?
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"""
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from __future__ import print_function
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from math import sqrt
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try:
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raw_input # Python 2
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except NameError:
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raw_input = input # Python 3
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def isprime(n):
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if n == 2:
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return True
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elif n % 2 == 0:
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return False
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else:
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sq = int(sqrt(n)) + 1
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for i in range(3, sq, 2):
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if n % i == 0:
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return False
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return True
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def solution(n):
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"""Returns the n-th prime number.
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>>> solution(6)
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13
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>>> solution(1)
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2
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>>> solution(3)
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5
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>>> solution(20)
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71
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>>> solution(50)
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229
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>>> solution(100)
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541
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"""
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i = 0
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j = 1
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while i != n and j < 3:
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j += 1
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if isprime(j):
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i += 1
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while i != n:
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j += 2
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if isprime(j):
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i += 1
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return j
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if __name__ == "__main__":
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print(solution(int(raw_input().strip())))
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