From 5736f8d4a21b51c47b7f47ca5ccb62f4fb9f651b Mon Sep 17 00:00:00 2001
From: Ettore Dreucci <ettore.dreucci@gmail.com>
Date: Tue, 22 Dec 2020 14:20:02 +0100
Subject: [PATCH] AoC 2020: day22

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>
---
 2020-python/inputs/day_22       |  53 +++++++++++++++
 2020-python/solutions/day_22.py | 110 ++++++++++++++++++++++++++++++++
 README.md                       |   1 +
 3 files changed, 164 insertions(+)
 create mode 100644 2020-python/inputs/day_22
 create mode 100644 2020-python/solutions/day_22.py

diff --git a/2020-python/inputs/day_22 b/2020-python/inputs/day_22
new file mode 100644
index 0000000..f854947
--- /dev/null
+++ b/2020-python/inputs/day_22
@@ -0,0 +1,53 @@
+Player 1:
+1
+43
+24
+34
+13
+7
+10
+36
+14
+12
+47
+32
+11
+3
+9
+25
+37
+21
+2
+45
+26
+8
+23
+6
+49
+
+Player 2:
+44
+5
+46
+18
+39
+50
+4
+41
+17
+28
+30
+42
+33
+38
+35
+22
+16
+27
+40
+48
+19
+29
+15
+31
+20
diff --git a/2020-python/solutions/day_22.py b/2020-python/solutions/day_22.py
new file mode 100644
index 0000000..265e9ba
--- /dev/null
+++ b/2020-python/solutions/day_22.py
@@ -0,0 +1,110 @@
+"""AOC 2020 Day 22"""
+
+import pathlib
+import time
+import collections
+import itertools
+
+TEST_INPUT = """Player 1:
+9
+2
+6
+3
+1
+
+Player 2:
+5
+8
+4
+7
+10"""
+
+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) -> tuple:
+    """take input data and return the appropriate data structure"""
+    deck1, deck2 = input_data.split('\n\n')
+    deck1, deck2 = deck1.splitlines(), deck2.splitlines()
+    deck1 = collections.deque(map(int, deck1[1:]))
+    deck2 = collections.deque(map(int, deck2[1:]))
+
+    return deck1, deck2
+
+def play_space_cards(deck1: collections.deque, deck2: collections.deque) -> collections.deque:
+    """return the winner's deck after a space cards game"""
+    assert len(deck1) == len(deck2)
+    while deck1 and deck2:
+        card1, card2 = deck1.popleft(), deck2.popleft()
+        assert card1 != card2
+        if card1 > card2:
+            deck1.extend((card1, card2))
+        else:
+            deck2.extend((card2, card1))
+
+    return deck1 if deck1 else deck2
+
+def play_recursive_space_cards(deck1: collections.deque, deck2: collections.deque) -> tuple:
+    """return the winner and its deck after a recursive space cards game"""
+    configurations = set()
+
+    while deck1 and deck2:
+        current_config = (tuple(deck1), tuple(deck2))
+        if current_config in configurations:
+            return 1, deck1
+        configurations.add(current_config)
+
+        card1, card2 = deck1.popleft(), deck2.popleft()
+        assert card1 != card2
+        if card1 <= len(deck1) and card2 <= len(deck2):
+            sub_deck1 = collections.deque(itertools.islice(deck1, card1))
+            sub_deck2 = collections.deque(itertools.islice(deck2, card2))
+            winner, _ = play_recursive_space_cards(sub_deck1, sub_deck2)
+        else:
+            winner = 1 if card1 > card2 else 2
+
+        if winner == 1:
+            deck1.extend((card1, card2))
+        else:
+            deck2.extend((card2, card1))
+
+    return (1, deck1) if deck1 else (2, deck2)
+
+def part1(entries: tuple) -> int:
+    """part1 solver"""
+    deck1, deck2 = entries[0].copy(), entries[1].copy()
+    winner = play_space_cards(deck1, deck2)
+    return sum(index * card for index, card in enumerate(reversed(winner), 1))
+
+def part2(entries: tuple) -> str:
+    """part2 solver"""
+    deck1, deck2 = entries
+    _, winner = play_recursive_space_cards(deck1, deck2)
+    return sum(index * card for index, card in enumerate(reversed(winner), 1))
+
+def test_input_day_22():
+    """pytest testing function"""
+    entries = extract(TEST_INPUT)
+    assert part1(entries) == 306
+    assert part2(entries) == 291
+
+def test_bench_day_22(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: %s" % part2(entries))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()
diff --git a/README.md b/README.md
index f4a85ce..6ce50ab 100644
--- a/README.md
+++ b/README.md
@@ -31,3 +31,4 @@
 | [Day 19](https://adventofcode.com/2020/day/19) | [145.980ms](./2020-python/solutions/day_19.py) | [259.030ms](./2020-python/solutions/day_19.py) |
 | [Day 20](https://adventofcode.com/2020/day/19) |                                                |                                                |
 | [Day 21](https://adventofcode.com/2020/day/21) | [2.177ms](./2020-python/solutions/day_21.py)   | [1.578ms](./2020-python/solutions/day_21.py)   |
+| [Day 22](https://adventofcode.com/2020/day/22) | [1.516s](./2020-python/solutions/day_22.py)    | [1.353s](./2020-python/solutions/day_22.py)    |