From 6f3d14caada6594ed5b62740cdc42e51a0ebc591 Mon Sep 17 00:00:00 2001
From: Ettore Dreucci <ettore.dreucci@gmail.com>
Date: Tue, 15 Dec 2020 09:42:24 +0100
Subject: [PATCH] AoC 2020: day15

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>
---
 2020-python/inputs/day_15       |  1 +
 2020-python/solutions/day_15.py | 75 +++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)
 create mode 100644 2020-python/inputs/day_15
 create mode 100644 2020-python/solutions/day_15.py

diff --git a/2020-python/inputs/day_15 b/2020-python/inputs/day_15
new file mode 100644
index 0000000..1c63dd2
--- /dev/null
+++ b/2020-python/inputs/day_15
@@ -0,0 +1 @@
+5,2,8,16,18,0,1
diff --git a/2020-python/solutions/day_15.py b/2020-python/solutions/day_15.py
new file mode 100644
index 0000000..9755c4e
--- /dev/null
+++ b/2020-python/solutions/day_15.py
@@ -0,0 +1,75 @@
+"""AOC 2020 Day 15"""
+
+import pathlib
+import time
+
+TEST_INPUT = """3,1,2"""
+
+def read_input(input_path: str) -> str:
+    """take input file path and return a str with the file's content"""
+    with open(input_path, 'r') as input_file:
+        input_data = input_file.read().strip()
+        return input_data
+
+def extract(input_data: str) -> list:
+    """take input data and return the appropriate data structure"""
+    entries = input_data.split(',')
+    return entries
+
+def part1(entries: dict) -> int:
+    """part1 solver"""
+    spoken = dict()
+    last_spoken = '-1'
+    for turn, number in enumerate(entries, 1):
+        spoken[number] = [turn]
+        last_spoken = number
+    for i in range(len(entries)+1, 2020+1):
+        if len(spoken.get(last_spoken, [])) < 2:
+            spoken.setdefault('0', []).append(i)
+            last_spoken = '0'
+        else:
+            number = str(int(spoken[last_spoken][-1]) - int(spoken[last_spoken][-2]))
+            spoken.setdefault(number, []).append(i)
+            last_spoken = number
+    return int(last_spoken)
+
+def part2(entries: tuple) -> int:
+    """part2 solver"""
+    spoken = dict()
+    last_spoken = '-1'
+    for turn, number in enumerate(entries, 1):
+        spoken[number] = [turn]
+        last_spoken = number
+    for i in range(len(entries)+1, 30000000+1):
+        if len(spoken.get(last_spoken, [])) < 2:
+            spoken.setdefault('0', []).append(i)
+            last_spoken = '0'
+        else:
+            number = str(int(spoken[last_spoken][-1]) - int(spoken[last_spoken][-2]))
+            spoken.setdefault(number, []).append(i)
+            last_spoken = number
+    return int(last_spoken)
+
+def test_input_day_15():
+    """pytest testing function"""
+    entries = extract(TEST_INPUT)
+    assert part1(entries) == 1836
+    assert part2(entries) == 362
+
+def test_bench_day_15(benchmark):
+    """pytest-benchmark function"""
+    benchmark(main)
+
+def main():
+    """main function"""
+    input_path = str(pathlib.Path(__file__).resolve().parent.parent) + "/inputs/" + str(pathlib.Path(__file__).stem)
+    start_time = time.time()
+    input_data = read_input(input_path)
+    entries = extract(input_data)
+    print("Part 1: %d" % part1(entries))
+    print("Part 2: %d" % part2(entries))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()