From 0fc5acbc43ef754cc23e9cfb54fe456ee26f75c2 Mon Sep 17 00:00:00 2001
From: Matt Walker <matt@suckerfish.net>
Date: Sun, 13 Dec 2020 20:51:36 -0800
Subject: [PATCH] 2020 Day 13 Part 1

---
 2020/13/Makefile         | 34 +++++++++++++++++++++++++
 2020/13/input-full.txt   |  2 ++
 2020/13/input-sample.txt |  2 ++
 2020/13/main.py          | 55 ++++++++++++++++++++++++++++++++++++++++
 2020/13/pyproject.toml   |  3 +++
 5 files changed, 96 insertions(+)
 create mode 100644 2020/13/Makefile
 create mode 100644 2020/13/input-full.txt
 create mode 100644 2020/13/input-sample.txt
 create mode 100644 2020/13/main.py
 create mode 100644 2020/13/pyproject.toml

diff --git a/2020/13/Makefile b/2020/13/Makefile
new file mode 100644
index 0000000..7a74a91
--- /dev/null
+++ b/2020/13/Makefile
@@ -0,0 +1,34 @@
+.PHONY: all
+all: full
+
+.PHONY: full
+full:
+	@python main.py input-full.txt
+
+.PHONY: full-debug
+full-debug:
+	@python main.py --debug input-full.txt
+
+.PHONY: sample
+sample:
+	@python main.py input-sample.txt
+
+.PHONY: sample-debug
+sample-debug:
+	@python main.py --debug input-sample.txt
+
+.PHONY: format
+format:
+	@black .
+
+.PHONY: lint
+lint:
+	@black --check .
+
+.PHONY: type-check
+type-check:
+	@mypy .
+
+.PHONY: test
+test:
+	@pytest .
diff --git a/2020/13/input-full.txt b/2020/13/input-full.txt
new file mode 100644
index 0000000..1ccfd8b
--- /dev/null
+++ b/2020/13/input-full.txt
@@ -0,0 +1,2 @@
+1000509
+17,x,x,x,x,x,x,x,x,x,x,37,x,x,x,x,x,739,x,29,x,x,x,x,x,x,x,x,x,x,13,x,x,x,x,x,x,x,x,x,23,x,x,x,x,x,x,x,971,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,19
diff --git a/2020/13/input-sample.txt b/2020/13/input-sample.txt
new file mode 100644
index 0000000..d76f619
--- /dev/null
+++ b/2020/13/input-sample.txt
@@ -0,0 +1,2 @@
+939
+7,13,x,x,59,x,31,19
diff --git a/2020/13/main.py b/2020/13/main.py
new file mode 100644
index 0000000..dbfb093
--- /dev/null
+++ b/2020/13/main.py
@@ -0,0 +1,55 @@
+import argparse
+from math import gcd
+from typing import List
+
+parser = argparse.ArgumentParser(description='Run an Advent of Code program')
+parser.add_argument(
+    'input_file', type=str, help='the file containing input data'
+)
+parser.add_argument(
+    '--debug', action='store_true', help='print debug messages'
+)
+args = parser.parse_args()
+
+
+def debug(log):
+    if args.debug:
+        print(log)
+
+
+input_data: List = []
+with open(args.input_file) as f:
+    input_data = [line for line in f.read().splitlines()]
+
+earliest_ts = int(input_data[0])
+numbered_buses = [
+    int(bus_id) for bus_id in input_data[1].split(',') if bus_id != 'x'
+]
+
+debug(f'{earliest_ts}: {numbered_buses}')
+
+earliest_bus = 0
+least_wait_time = 99999999999
+for bus in numbered_buses:
+    wait_time = bus - (earliest_ts % bus)
+    debug(f'{bus}: {wait_time}')
+    if wait_time < least_wait_time:
+        earliest_bus = bus
+        least_wait_time = wait_time
+
+print(f'Part 1: {earliest_bus * least_wait_time}')
+
+all_buses = [
+    (index, int(bus_id))
+    for index, bus_id in enumerate(input_data[1].split(','))
+    if bus_id != 'x'
+]
+
+
+def lcm(a, b):
+    return abs(a * b) // gcd(a, b)
+
+
+debug(all_buses)
+debug(gcd(13, 7))
+debug(lcm(13, 7))
diff --git a/2020/13/pyproject.toml b/2020/13/pyproject.toml
new file mode 100644
index 0000000..d3728ba
--- /dev/null
+++ b/2020/13/pyproject.toml
@@ -0,0 +1,3 @@
+[tool.black]
+line-length = 79
+skip-string-normalization = true