advent_of_code_day1.py

# http://adventofcode.com/2016/day/1

import re
import numpy as np


def taxi_dist(S):
    p = [0, 0]
    i = 0
    d = 1
    for x in S:
        if (i == 0 and x[0] == 'L') or (i == 1 and x[0] == 'R'):
            d *= -1
        p[i] += int(x[1:]) * d
        i += 1
        i %= 2
    return np.sum(np.abs(p))


def visit_twice(S):
    p = [0, 0]
    q = [0, 0]
    i = 0
    d = 1
    Q = {tuple(q)}
    for x in S:
        if (i == 0 and x[0] == 'L') or (i == 1 and x[0] == 'R'):
            d *= -1
        e = int(x[1:])
        j = i + 1
        j %= 2
        for k in range(e):
            p[i] += d
            q[j] += d
            if tuple(q) in Q:
                return np.sum(np.abs(p))
            Q.add(tuple(q))
        i += 1
        i %= 2



s = "R3, L5, R1, R2, L5, R2, R3, L2, L5, R5, L4, L3, R5, L1, R3, R4, R1, L3, R3, L2, L5, L2, R4, R5, R5, L4, L3, L3, R4, R4, R5, L5, L3, R2, R2, L3, L4, L5, R1, R3, L3, R2, L3, R5, L194, L2, L5, R2, R1, R1, L1, L5, L4, R4, R2, R2, L4, L1, R2, R53, R3, L5, R72, R2, L5, R3, L4, R187, L4, L5, L2, R1, R3, R5, L4, L4, R2, R5, L5, L4, L3, R5, L2, R1, R1, R4, L1, R2, L3, R5, L4, R2, L3, R1, L4, R4, L1, L2, R3, L1, L1, R4, R3, L4, R2, R5, L2, L3, L3, L1, R3, R5, R2, R3, R1, R2, L1, L4, L5, L2, R4, R5, L2, R4, R4, L3, R2, R1, L4, R3, L3, L4, L3, L1, R3, L2, R2, L4, L4, L5, R3, R5, R3, L2, R5, L2, L1, L5, L1, R2, R4, L5, R2, L4, L5, L4, L5, L2, L5, L4, R5, R3, R2, R2, L3, R3, L2, L5"
#s = "R2, L3"
# s = "R2 R2 R2"
# s = "R5, L5, R5, R3"
# s = "R8, R4, R4, R8"
S = re.split('\W+', s)

print(taxi_dist(S))
print(visit_twice(S))