advent-of-code/2023/day9.py

import sys

lines = sys.stdin.read().splitlines()

data = [[int(c) for c in line.split()] for line in lines]

right_values: list[int] = []
left_values: list[int] = []
for values in data:
    diffs = [values]
    while any(d != 0 for d in diffs[-1]):
        diffs.append([rhs - lhs for lhs, rhs in zip(diffs[-1][:-1], diffs[-1][1:])])

    rhs: list[int] = [0]
    lhs: list[int] = [0]
    for cx in range(len(diffs) - 1):
        rhs.append(diffs[-cx - 2][-1] + rhs[cx])
        lhs.append(diffs[-cx - 2][0] - lhs[cx])

    right_values.append(rhs[-1])
    left_values.append(lhs[-1])

# part 1
answer_1 = sum(right_values)
print(f"answer 1 is {answer_1}")

# part 2
answer_2 = sum(left_values)
print(f"answer 2 is {answer_2}")