path: root/day24.py

#!/usr/bin/env python

with open('day24.txt') as data:
    program = [tuple(line.strip().split()) for line in data]
    params = []
    for i in range(0, 18 * 14, 18):
        a = int(program[i+4][-1])
        b = int(program[i+5][-1])
        c = int(program[i+15][-1])
        params.append((a, b, c))


def f(params, z, w):
    a, b, c = params
    if z % 26 + b != w:
        z = z//a*26 + w + c
    else:
        z = z//a
    return z

zs = {0: [0, 0]}
for i, p in enumerate(params):
    new_zs = {}
    for z, inp in zs.items():
        for w in range(1, 10):
            new_z = f(p, z, w)
            if p[0] == 1 or (p[0] == 26 and new_z < z):
                if new_z not in new_zs:
                    new_zs[new_z] = [inp[0]*10+w, inp[1]*10+w]
                else:
                    new_zs[new_z][0] = min(new_zs[new_z][0], inp[0]*10+w)
                    new_zs[new_z][1] = max(new_zs[new_z][1], inp[1]*10+w)
    print(f"Digit: {i+1} tracked values of z: {len(new_zs)}")
    zs = new_zs
print(f'best valid values: {zs[0]}')