AoC 2020: day23

Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>

2020-python/inputs/day_23

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+589174263

2020-python/solutions/day_23.py

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+"""AOC 2020 Day 23"""
+
+import pathlib
+import time
+
+TEST_INPUT = """389125467"""
+
+class Cup:
+    """a cup with a value and a pointer to the next cup"""
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+
+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"""
+    return list(map(int, input_data))
+
+def build_list(values: list, n_cups: int = None) -> tuple:
+    """return the value of the first cup and a dict of Cup"""
+    if n_cups is None:
+        n_cups = len(values)
+    cups_list = [None]*(n_cups+1)
+    for i in range(1, n_cups+1):
+        cups_list[i] = Cup(i)
+
+    for i, _ in enumerate(values):
+        cups_list[values[i]].next = cups_list[values[(i+1)%len(values)]]
+
+    return values[0], cups_list
+
+def play_crab_cups(first_cup: int, cups: list, moves: int):
+    """play n moves of crab cups"""
+    current = cups[first_cup]
+    max_cup = len(cups) - 1
+    for _ in range(moves):
+        next_cup = current.next
+        picked = (next_cup.value, next_cup.next.value, next_cup.next.next.value)
+        current.next = current.next.next.next.next
+        label = current.value
+
+        while label in picked or label == current.value:
+            if label != 1:
+                label = label-1
+            else:
+                label = max_cup
+
+        destination = cups[label]
+        next_cup.next.next.next = destination.next
+        destination.next = next_cup
+        current = current.next
+
+def part1(entries: list) -> str:
+    """part1 solver"""
+    first_cup, cups = build_list(entries)
+    play_crab_cups(first_cup, cups, 100)
+
+    cur_cup = cups[1]
+    cups_str = ''
+    for _ in range(8):
+        cur_cup = cur_cup.next
+        cups_str += str(cur_cup.value)
+
+    return cups_str
+
+def part2(entries: list) -> int:
+    """part2 solver"""
+    entries.extend(range(10, 1000001))
+    first_cup, cups = build_list(entries)
+    play_crab_cups(first_cup, cups, 10000000)
+
+    return cups[1].next.value * cups[1].next.next.value
+
+def test_input_day_23():
+    """pytest testing function"""
+    entries = extract(TEST_INPUT)
+    assert part1(entries) == '67384529'
+    assert part2(entries) == 149245887792
+
+def test_bench_day_23(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: %s" % part1(entries))
+    print("Part 2: %s" % part2(entries))
+    end_time = time.time()
+    print("Execution time: %f" % (end_time-start_time))
+
+if __name__ == "__main__":
+    main()

README.md

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 | [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)    |
+| [Day 23](https://adventofcode.com/2020/day/23) | [14.754s](./2020-python/solutions/day_23.py)   | [3.572s](./2020-python/solutions/day_23.py)    |