aoc2015/d03/part2.py

import sys

s = sys.stdin.read()[:-1]

cpS = (0,0)
cpR = (0,0)
P = {cpS}

dep = {
    '<':(1,0),
    '>':(-1,0),
    'v':(0,1),
    '^':(0,-1),
  }

for i,c in enumerate(s):
    dx,dy = dep[c]
    if i%2:
        x,y = cpS
        cpS = (x+dx,y+dy)
        P.add(cpS)
    else:
        x,y = cpR
        cpR = (x+dx,y+dy)
        P.add(cpR)

print(len(P))