https://adventofcode.com/2023/day/19

day19.py

import re

wf, pt = open(0).read().split('\n\n')

wfd = {}
for l in wf.split():
    w, cs = l.split('{')
    cd = list()
    conds = cs[:-1].split(',')
    for i, c in enumerate(conds):
        if i+1==len(conds):
            cd.append((c, )+(None, )*3)
            break
        k, dest = c.split(':')
        f, v = re.split(r'[<>]', k)
        cd.append((dest, f, '<' in k, int(v)))
    wfd[w] = cd
wfd['A'] = [('A', )+(None, )*3]
wfd['R'] = [('R', )+(None, )*3]

pd = []
for l in pt.split():
    props = l[1:-1].split(',')
    part = dict()
    for p in props:
        k, v = p.split('=')
        part[k] = int(v)
    pd.append(part)

ans = 0
for part in pd:
    cs = 'in'
    while cs not in ['A', 'R']:
        cds = wfd[cs]
        for dest, f, less, cv in cds[:-1]:
            v = part[f]
            if less and v<cv:
                cs = dest
                break
            elif not less and v>cv:
                cs = dest
                break
        else:
            cs = cds[-1][0]
    if cs=='A':
        ans += sum(part.values())

print(ans)


def shrink(xlh, f, rs):
    xl, xh = xlh
    ans = []
    for r in rs:
        x, y = r[f]
        x, y = max(xl, x), min(xh, y)
        if x>=y: continue
        r[f] = x, y
        ans.append(r)
    return ans


def dfs(cs):
    dest, f, less, v = cs[0]
    if f is None and dest=='R': return []
    if f is None and dest=='A': return [dict((c, (1, 4001)) for c in 'xmas')]
    if f is None: return dfs(wfd[dest])
    rs1 = shrink((1, v) if less else (v+1, 4001), f, dfs(wfd[dest]))  # accept
    rs2 = shrink((v, 4001) if less else (1, v+1), f, dfs(cs[1:]))  # reject
    return rs1+rs2


ans = 0
for d in dfs([('in', )+(None, )*3]):
    p = 1
    for l, r in d.values():
        p *= r-l
    ans += p
print(ans)