Problem 15

Problem: 

Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.

How many such routes are there through a 20×20 grid?


My Solution:


from scipy.special import comb
# This solution uses combinatoric approach
# the idea is we must make 40 moves in total, 20 of which must be down.
# How many ways to do that? well 40 choose 20.
print (comb(40,20))