Day 13 Part 1

Author: monpie3

Day_13/README.md

@@ -0,0 +1,56 @@
+## \--- Day 13: Claw Contraption ---
+
+Next up: the [lobby](https://adventofcode.com/2020/day/24) of a resort on a tropical island. The Historians take a moment to admire the hexagonal floor tiles before spreading out.
+
+Fortunately, it looks like the resort has a new [arcade](https://en.wikipedia.org/wiki/Amusement_arcade)! Maybe you can win some prizes from the [claw machines](https://en.wikipedia.org/wiki/Claw_machine)?
+
+The claw machines here are a little unusual. Instead of a joystick or directional buttons to control the claw, these machines have two buttons labeled `A` and `B`. Worse, you can't just put in a token and play; it costs _3 tokens_ to push the `A` button and _1 token_ to push the `B` button.
+
+With a little experimentation, you figure out that each machine's buttons are configured to move the claw a specific amount to the _right_ (along the `X` axis) and a specific amount _forward_ (along the `Y` axis) each time that button is pressed.
+
+Each machine contains one _prize_; to win the prize, the claw must be positioned _exactly_ above the prize on both the `X` and `Y` axes.
+
+You wonder: what is the smallest number of tokens you would have to spend to win as many prizes as possible? You assemble a list of every machine's button behavior and prize location (your puzzle input). For example:
+
+```
+Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279
+```
+
+This list describes the button configuration and prize location of four different claw machines.
+
+For now, consider just the first claw machine in the list:
+
+- Pushing the machine's `A` button would move the claw `94` units along the `X` axis and `34` units along the `Y` axis.
+- Pushing the `B` button would move the claw `22` units along the `X` axis and `67` units along the `Y` axis.
+- The prize is located at `X=8400`, `Y=5400`; this means that from the claw's initial position, it would need to move exactly `8400` units along the `X` axis and exactly `5400` units along the `Y` axis to be perfectly aligned with the prize in this machine.
+
+The cheapest way to win the prize is by pushing the `A` button `80` times and the `B` button `40` times. This would line up the claw along the `X` axis (because `80*94 + 40*22 = 8400`) and along the `Y` axis (because `80*34 + 40*67 = 5400`). Doing this would cost `80*3` tokens for the `A` presses and `40*1` for the `B` presses, a total of `280` tokens.
+
+For the second and fourth claw machines, there is no combination of A and B presses that will ever win a prize.
+
+For the third claw machine, the cheapest way to win the prize is by pushing the `A` button `38` times and the `B` button `86` times. Doing this would cost a total of `200` tokens.
+
+So, the most prizes you could possibly win is two; the minimum tokens you would have to spend to win all (two) prizes is `480`.
+
+You estimate that each button would need to be pressed _no more than `100` times_ to win a prize. How else would someone be expected to play?
+
+Figure out how to win as many prizes as possible. _What is the fewest tokens you would have to spend to win all possible prizes?_
+
+Your puzzle answer was `[REDACTED]`.
+
+The first half of this puzzle is complete! It provides one gold star: ⭐
+

Day_13/example_13a.txt

@@ -0,0 +1,15 @@
+Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279

Day_13/task_13a.py

@@ -0,0 +1,48 @@
+import re
+from sympy import symbols, Eq, solve
+
+A_PRICE = 3
+B_PRICE = 1
+
+
+def load_data(filename):
+    with open(filename, "r") as f:
+        data = f.read().split("\n\n")
+
+    machines = []
+    for machine in data:
+        machine = re.findall(r"\d+", machine)
+        machine = list(map(int, machine))
+        machines.append(machine)
+
+    return machines
+
+
+def find_way_to_win(machine):
+    a1, a2, b1, b2, r1, r2 = machine
+
+    x, y = symbols("x,y")
+    eq1 = Eq((a1 * x + b1 * y), r1)
+    eq2 = Eq((a2 * x + b2 * y), r2)
+
+    sol_dict = solve((eq1, eq2), (x, y))
+    x = sol_dict[x]
+    y = sol_dict[y]
+
+    if x == int(x) and y == int(y):
+        return x, y
+    else:
+        return 0, 0
+
+
+def calculate_tokens(machines):
+    token = 0
+    for machine in machines:
+        a, b = find_way_to_win(machine)
+        token += a * A_PRICE + b * B_PRICE
+    return token
+
+
+if "__main__" == __name__:
+    machines = load_data("Day_13/puzzle_input.txt")
+    print(calculate_tokens(machines))

Day_13/test_task_13a.py

@@ -0,0 +1,13 @@
+from task_13a import load_data, calculate_tokens
+import pytest
+
+
+@pytest.mark.parametrize(
+    "file_path, expected",
+    [
+        ("Day_13/example_13a.txt", 480),
+    ],
+)
+def test_calculate_tokens(file_path, expected):
+    machines = load_data(file_path)
+    assert calculate_tokens(machines) == expected

requirements.txt

@@ -0,0 +1 @@
+sympy==1.13.3