diff --git a/Project Euler/Problem 15/sol1.py b/Project Euler/Problem 15/sol1.py new file mode 100644 index 000000000..9b61b37d2 --- /dev/null +++ b/Project Euler/Problem 15/sol1.py @@ -0,0 +1,20 @@ +from __future__ import print_function +from math import factorial, ceil + +def lattice_paths(n): + n = 2*n #middle entry of odd rows starting at row 3 is the solution for n = 1, 2, 3,... + k = n/2 + + return factorial(n)/(factorial(k)*factorial(n-k)) + +if __name__ == '__main__': + import sys + + if len(sys.argv) == 1: + print(lattice_paths(20)) + else: + try: + n = int(sys.argv[1]) + print(lattice_paths(n)) + except ValueError: + print('Invalid entry - please enter a number.')