mirror of
https://github.com/python/cpython.git
synced 2025-11-04 03:44:55 +00:00
49 lines
1.1 KiB
Python
Executable file
49 lines
1.1 KiB
Python
Executable file
#! /usr/bin/env python
|
|
|
|
# Factorize numbers.
|
|
# The algorithm is not efficient, but easy to understand.
|
|
# If there are large factors, it will take forever to find them,
|
|
# because we try all odd numbers between 3 and sqrt(n)...
|
|
|
|
import sys
|
|
from math import sqrt
|
|
|
|
error = 'fact.error' # exception
|
|
|
|
def fact(n):
|
|
if n < 1: raise error # fact() argument should be >= 1
|
|
if n == 1: return [] # special case
|
|
res = []
|
|
# Treat even factors special, so we can use i = i+2 later
|
|
while n%2 == 0:
|
|
res.append(2)
|
|
n = n/2
|
|
# Try odd numbers up to sqrt(n)
|
|
limit = sqrt(float(n+1))
|
|
i = 3
|
|
while i <= limit:
|
|
if n%i == 0:
|
|
res.append(i)
|
|
n = n/i
|
|
limit = sqrt(n+1)
|
|
else:
|
|
i = i+2
|
|
if n != 1:
|
|
res.append(n)
|
|
return res
|
|
|
|
def main():
|
|
if len(sys.argv) > 1:
|
|
for arg in sys.argv[1:]:
|
|
n = eval(arg)
|
|
print n, fact(n)
|
|
else:
|
|
try:
|
|
while 1:
|
|
n = input()
|
|
print n, fact(n)
|
|
except EOFError:
|
|
pass
|
|
|
|
if __name__ == "__main__":
|
|
main()
|