mirror of
https://github.com/rasbt/python_reference.git
synced 2024-11-27 14:01:15 +00:00
71 lines
2.1 KiB
Python
Executable File
71 lines
2.1 KiB
Python
Executable File
#!/usr/bin/env python
|
|
|
|
# Sebastian Raschka 2014
|
|
# Functions to calculate factorial, combinations, and permutations
|
|
# bundled in an simple command line interface.
|
|
|
|
def factorial(n):
|
|
if n == 0:
|
|
return 1
|
|
else:
|
|
return n * factorial(n-1)
|
|
|
|
def combinations(n, r):
|
|
numerator = factorial(n)
|
|
denominator = factorial(r) * factorial(n-r)
|
|
return int(numerator/denominator)
|
|
|
|
def permutations(n, r):
|
|
numerator = factorial(n)
|
|
denominator = factorial(n-r)
|
|
return int(numerator/denominator)
|
|
|
|
assert(factorial(3) == 6)
|
|
assert(combinations(20, 8) == 125970)
|
|
assert(permutations(30, 3) == 24360)
|
|
|
|
|
|
|
|
|
|
if __name__ == '__main__':
|
|
|
|
import argparse
|
|
parser = argparse.ArgumentParser(
|
|
description='Script to calculate the number of combinations or permutations ("n choose r")',
|
|
formatter_class=argparse.RawTextHelpFormatter,
|
|
|
|
prog='Combinations',
|
|
epilog='Example: ./combinations.py -c 20 3'
|
|
)
|
|
|
|
parser.add_argument('-c', '--combinations', type=int, metavar='NUMBER', nargs=2,
|
|
help='Combinations: Number of ways to combine n items with sequence length r where the item order does not matter.')
|
|
|
|
parser.add_argument('-p', '--permutations', type=int, metavar='NUMBER', nargs=2,
|
|
help='Permutations: Number of ways to combine n items with sequence length r where the item order does not matter.')
|
|
|
|
parser.add_argument('-f', '--factorial', type=int, metavar='NUMBER', help='n! e.g., 5! = 5*4*3*2*1 = 120.')
|
|
|
|
parser.add_argument('--version', action='version', version='%(prog)s 1.0')
|
|
|
|
args = parser.parse_args()
|
|
|
|
if not any((args.combinations, args.permutations, args.factorial)):
|
|
parser.print_help()
|
|
quit()
|
|
|
|
if args.factorial:
|
|
print(factorial(args.factorial))
|
|
|
|
if args.combinations:
|
|
print(combinations(args.combinations[0], args.combinations[1]))
|
|
|
|
if args.permutations:
|
|
print(permutations(args.permutations[0], args.permutations[1]))
|
|
|
|
if args.factorial:
|
|
print(factorial(args.factorial))
|
|
|
|
|
|
|
|
|