48 lines
1.1 KiB
Python
Executable File
48 lines
1.1 KiB
Python
Executable File
#! /usr/bin/env python
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# Factorize numbers.
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# The algorithm is not efficient, but easy to understand.
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# If there are large factors, it will take forever to find them,
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# because we try all odd numbers between 3 and sqrt(n)...
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import sys
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from math import sqrt
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def fact(n):
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if n < 1: raise ValueError # fact() argument should be >= 1
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if n == 1: return [] # special case
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res = []
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# Treat even factors special, so we can use i = i+2 later
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while n%2 == 0:
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res.append(2)
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n = n//2
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# Try odd numbers up to sqrt(n)
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limit = sqrt(float(n+1))
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i = 3
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while i <= limit:
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if n%i == 0:
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res.append(i)
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n = n//i
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limit = sqrt(n+1)
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else:
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i = i+2
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if n != 1:
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res.append(n)
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return res
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def main():
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if len(sys.argv) > 1:
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for arg in sys.argv[1:]:
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n = eval(arg)
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print n, fact(n)
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else:
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try:
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while 1:
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n = input()
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print n, fact(n)
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except EOFError:
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pass
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if __name__ == "__main__":
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main()
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