problem018.py

# By starting at the top of the triangle below and moving to adjacent numbers on the row below,
# the maximum total from top to bottom is 23.
#
# 3
# 7 4
# 2 4 6
# 8 5 9 3
#
# That is, 3 + 7 + 4 + 9 = 23.
#
# Find the maximum total from top to bottom of the triangle below:
#
# 75
# 95 64
# 17 47 82
# 18 35 87 10
# 20 04 82 47 65
# 19 01 23 75 03 34
# 88 02 77 73 07 63 67
# 99 65 04 28 06 16 70 92
# 41 41 26 56 83 40 80 70 33
# 41 48 72 33 47 32 37 16 94 29
# 53 71 44 65 25 43 91 52 97 51 14
# 70 11 33 28 77 73 17 78 39 68 17 57
# 91 71 52 38 17 14 91 43 58 50 27 29 48
# 63 66 04 68 89 53 67 30 73 16 69 87 40 31
# 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
#
# NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route.
# However, Problem 67, is the same challenge with a triangle containing one-hundred rows;
# it cannot be solved by brute force, and requires a clever method! ;o)

with open("input_data/problem018_input.txt") as f:
    pyr = f.read().split("\n")
    for i, row in enumerate(pyr):
        pyr[i] = [int(j) for j in row.split(" ")]

helper_pyr = pyr[::-1]

for i, row in enumerate(pyr[::-1]):
    if not (i == 0 or i == (len(pyr)-1)):
        for j, number in enumerate(row):
            helper_pyr[i][j] = max(number+helper_pyr[i-1][j], number+helper_pyr[i-1][j+1])

helper_pyr = helper_pyr[::-1]
max_sum = helper_pyr[0][0] + max(helper_pyr[1])

print(max_sum)