#!/usr/bin/env python def count_trees(right, down, lines): n = 0 for i, line in enumerate(lines[::down]): c = line[(i*right) % len(line)] if c == '#': n += 1 return n if __name__ == '__main__': with open('input.txt', 'r') as f: lines = [line.strip() for line in f.readlines()] print(count_trees(3, 1, lines)) hits_multiplied = 1 for slope in ((1,1), (3,1), (5,1), (7,1), (1,2)): hits_multiplied *= count_trees(*slope, lines) print(hits_multiplied)