Advent of Code: Day #03 - Toboggan Trajectory

With our toboggan successfully rented we can set off to the airport but first we need to know how many trees are in the way on the slope down.

Given an infinitely repeating map of trees in the x dimension find how many trees the toboggan will hit on a slope of right 3, down 1 departing from top left to to the bottom of the input.

Reading in the data

Today I didn't do any pre-processing when reading in the data and simply added each line of the input data to an array.

def read_data(path):
    forest = []
    with open(path, "r") as file:
        for line in file.readlines():
            forest.append(line)
    return forest

The Solution

This problem can be solved by checking if the item at x, y position of the toboggan is a tree or not. Since the pattern is infinitely repeated in the x direction we can just use a modulo to wrap back round to other side of the input.

def task_one(dataset):
    tree_count = 0
    tree_height = len(dataset) - 1
    tree_width = len(dataset[0]) - 1
    pos = [3, 1]
    for _ in range(tree_height):
        if dataset[pos[1]][pos[0]] == "#":
            tree_count += 1
        pos[0] += 3
        pos[1] += 1
        pos[0] %= tree_width

    return tree_count

The Solution

Task two was the same as task apart from we had to count the trees for several different slopes and return the product.

def task_two(dataset):
    paths = [[1, 1], [3, 1], [5, 1], [7, 1], [1, 2]]
    total = 1
    for path in paths:
        tree_count = 0
        tree_height = len(dataset) - 1
        tree_width = len(dataset[0]) - 1
        pos = deepcopy(path)
        for _ in range(tree_height // pos[1]):
            if dataset[pos[1]][pos[0]] == "#":
                tree_count += 1
            pos[0] += path[0]
            pos[1] += path[1]
            pos[0] %= tree_width

        total *= tree_count

    return total