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21 lines
467 B
Python
21 lines
467 B
Python
from __future__ import print_function
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from math import factorial
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def lattice_paths(n):
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n = 2*n #middle entry of odd rows starting at row 3 is the solution for n = 1, 2, 3,...
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k = n/2
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return factorial(n)/(factorial(k)*factorial(n-k))
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if __name__ == '__main__':
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import sys
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if len(sys.argv) == 1:
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print(lattice_paths(20))
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else:
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try:
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n = int(sys.argv[1])
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print(lattice_paths(n))
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except ValueError:
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print('Invalid entry - please enter a number.')
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