advent_day_3.py

# http://adventofcode.com/day/3 - part 1
#
# instructions - String with sequentials commands for which direction to take.
# ^ north, v south, > east, < west
#
# Returns an integer of the area of wrapping paper required, in square feet.
def houses_visited_by_santa(instructions):
    visited = [[0, 0]]

    x = y = 0

    for move in list(instructions):
        if move == "^": # north
            y += 1
        elif move == "v": # south
            y -= 1
        elif move == ">": # east
            x += 1
        elif move == "<": # west
            x -= 1

        position = [x, y]

        if not position in visited:
            visited.append(position)

    return len(visited)

# http://adventofcode.com/day/3 - part 2
#
# instructions - String with sequentials commands for which direction to take.
# ^ north, v south, > east, < west
#
# Returns an integer of the area of wrapping paper required, in square feet.
def houses_visited_by_santa_and_robot(instructions):
    visited = [[0, 0]]

    santa = { 'x': 0, 'y': 0 }
    robot = { 'x': 0, 'y': 0 }

    for i, move in enumerate(list(instructions)):
        if i % 2 == 0:
            person = santa
        else:
            person = robot

        if move == "^": # north
            person['y'] += 1
        elif move == "v": # south
            person['y'] -= 1
        elif move == ">": # east
            person['x'] += 1
        elif move == "<": # west
            person['x'] -= 1

        position = [person['x'], person['y']]

        if not position in visited:
            visited.append(position)

    return len(visited)