day9

day9_part1.py

#!/usr/bin/env python3

def solve(arr: list[int]) -> int:
    n = len(arr)
    x = [arr]
    for i in range(n - 1):
        x.append([x[i][j + 1] - x[i][j] for j in range(n - i - 1)])
    x[-1].append(0)
    for i in range(n - 2, -1, -1):
        x[i].append(x[i][-1] + x[i + 1][-1])
    return x[0][-1]


with open("input.txt") as f:
    print(sum(solve([int(x) for x in line.split(" ")]) for line in f))

day9_part2.py

#!/usr/bin/env python3

def solve(arr: list[int]) -> int:
    arr.reverse()
    n = len(arr)
    x = [arr]
    for i in range(n - 1):
        x.append([x[i][j + 1] - x[i][j] for j in range(n - i - 1)])
    x[-1].append(0)
    for i in range(n - 2, -1, -1):
        x[i].append(x[i][-1] + x[i + 1][-1])
    return x[0][-1]


with open("input.txt") as f:
    print(sum(solve([int(x) for x in line.split(" ")]) for line in f))