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79 lines
1.9 KiB
Python
79 lines
1.9 KiB
Python
"""
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Problem:
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The prime factors of 13195 are 5,7,13 and 29. What is the largest prime factor
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of a given number N?
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e.g. for 10, largest prime factor = 5. For 17, largest prime factor = 17.
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"""
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import math
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def isprime(no):
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if no == 2:
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return True
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elif no % 2 == 0:
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return False
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sq = int(math.sqrt(no)) + 1
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for i in range(3, sq, 2):
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if no % 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 largest prime factor of a given number n.
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>>> solution(13195)
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29
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>>> solution(10)
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5
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>>> solution(17)
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17
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>>> solution(3.4)
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3
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>>> solution(0)
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Traceback (most recent call last):
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...
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ValueError: Parameter n must be greater or equal to one.
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>>> solution(-17)
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Traceback (most recent call last):
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...
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ValueError: Parameter n must be greater or equal to one.
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>>> solution([])
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Traceback (most recent call last):
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...
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TypeError: Parameter n must be int or passive of cast to int.
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>>> solution("asd")
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Traceback (most recent call last):
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...
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TypeError: Parameter n must be int or passive of cast to int.
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"""
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try:
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n = int(n)
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except (TypeError, ValueError) as e:
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raise TypeError("Parameter n must be int or passive of cast to int.")
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if n <= 0:
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raise ValueError("Parameter n must be greater or equal to one.")
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maxNumber = 0
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if isprime(n):
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return n
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else:
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while n % 2 == 0:
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n = n / 2
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if isprime(n):
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return int(n)
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else:
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n1 = int(math.sqrt(n)) + 1
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for i in range(3, n1, 2):
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if n % i == 0:
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if isprime(n / i):
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maxNumber = n / i
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break
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elif isprime(i):
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maxNumber = i
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return maxNumber
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if __name__ == "__main__":
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print(solution(int(input().strip())))
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