AoC 2020 Day 10

import operator as op, functools as ft
from collections import Counter
from more_itertools import pairwise

def aoc_2020_10(inp):

    difs= Counter()
    inp.append(max_el:= max(inp) + 3)
    inp.append(0)
    inp.sort()

    # part 1
    for i, j in pairwise(inp):
        difs[j-i]+= 1
    result_a= ft.reduce(op.mul, difs.values(), 1)

    # part 2
    found= 0
    def process(n, inp):
        nonlocal found
        if n == inp[-1]:
            found+= 1
            return
        for n1 in inp:
            if n+1 <= n1 <= n+3:
                process(n1, inp)
            if n1 > n+3:
                break

    factor= 1
    while inp:
        while len(inp) > 1 and inp[1] - inp[0] == 3:
            del inp[0]
        if len(inp) == 1: break
        for i in range(len(inp)-1):
            try:
                if inp[i+1] - inp[i] == 3:
                    found= 0
                    process(inp[0], inp[:i+1])
                    factor*= found
                    del inp[:i]
                    break
            except IndexError:
                del inp[0]
                break

    result_b= factor

    return result_a, result_b