Day 16 (Python)

.github/README.md

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16-ticketTranslation/README.md

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+# [Day 16: Ticket Translation](https://adventofcode.com/2020/day/16)
+
+It took me a long while to realise each column could have multiple different possibilities for which ticket field it could be.
+
+<details><summary>Script output</summary>
+
+```
+❯ python .\python\
+AoC 2020: day 16 - Ticket Translation
+Python 3.8.5
+
+Test cases
+1.1 pass
+2.1 pass
+
+Answers
+Part 1: 29019
+Part 2: 517827547723
+```
+
+</details>

16-ticketTranslation/info.json

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+{
+    "year": "2020",
+    "day": "16",
+    "title": "Ticket Translation",
+    "testCases": {
+        "one": [
+            {
+                "input": "class: 1-3 or 5-7\nrow: 6-11 or 33-44\nseat: 13-40 or 45-50\n\nyour ticket:\n7,1,14\n\nnearby tickets:\n7,3,47\n40,4,50\n55,2,20\n38,6,12",
+                "expected": 71
+            }
+        ],
+        "two": [
+            {
+                "input":"departure class: 0-1 or 4-19\nrow: 0-5 or 8-19\nseat: 0-13 or 16-19\n\nyour ticket:\n11,12,13\n\nnearby tickets:\n3,9,18\n15,1,5\n5,14,9\n",
+                "expected": 12
+            }
+        ]
+    }
+}

16-ticketTranslation/python/__main__.py

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+import json
+import platform
+import sys
+
+from rich import print
+
+from partOne import partOne
+from partTwo import partTwo
+
+
+def run_tests(test_cases):
+    do_tests = True
+    if len(test_cases) == 0:
+        do_tests = False
+    elif len(test_cases["one"]) == 0 and len(test_cases["two"]) == 0:
+        do_tests = False
+
+    if not do_tests:
+        print("Info: no test cases specified. Skipping tests\n")
+        return
+
+    print("Test cases")
+
+    def rt(tcs, f, n):
+        for i, tc in enumerate(tcs):
+            print(f"{n}.{i+1} ", end="")
+            expectedInt = tc["expected"]
+            result = f(str(tc["input"]))
+            if result == expectedInt:
+                print("[green]pass[/green]")
+            else:
+                print(f"[red]fail[/red] (got {result}, expected {expectedInt})")
+
+    rt(test_cases["one"], partOne, 1)
+    rt(test_cases["two"], partTwo, 2)
+
+    print()
+
+
+if __name__ == "__main__":
+    try:
+        info = open("info.json").read()
+    except FileNotFoundError:
+        print("Error: could not open info.json")
+        sys.exit(-1)
+
+    info = json.loads(info)
+
+    year = info["year"]
+    day = info["day"]
+    title = info["title"]
+
+    print(f"[yellow]AoC {year}[/yellow]: day {day} - {title}")
+    print(f"Python {platform.python_version()}\n")
+
+    try:
+        challenge_input = open("input.txt").read()
+    except FileNotFoundError:
+        print("Error: could not open input.txt")
+        sys.exit(-1)
+
+    if "vis" in sys.argv:
+        import visualise
+
+        print("[green]Running visualisation....[/green]")
+
+        visualise.visualise(challenge_input)
+        sys.exit()
+
+    run_tests(info["testCases"])
+
+    if "debug" in sys.argv:
+        sys.exit()
+
+    print("Answers")
+    print("Part 1:", partOne(challenge_input))
+    print("Part 2:", partTwo(challenge_input))

16-ticketTranslation/python/common.py

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+from typing import List, Tuple
+
+class Rule:
+    name: str
+    ranges: Tuple[int, ...]
+
+    def __init__(self, instr:str) -> None:
+        # arrival location: 26-482 or 504-959
+        field, conditions = instr.strip().split(": ")
+        self.name = field
+        ranges = conditions.split("or")
+        self.ranges = tuple([int(x) for x in ranges[0].strip().split("-")] + [int(x) for x in ranges[1].strip().split("-")])
+
+class Ticket:
+    fields: Tuple[int]
+
+    def __init__(self, instr:str) -> None:
+        self.fields = tuple([int(x) for x in instr.strip().split(",")])
+
+def parse(instr: str) -> Tuple[List[Rule], Ticket, List[Ticket]]:
+
+    raw_rules, raw_my_ticket, raw_other_tickets = instr.strip().split("\n\n")
+
+    rules = [Rule(x) for x in raw_rules.split("\n")]
+
+    my_ticket = Ticket(raw_my_ticket.split("\n")[-1])
+
+    other_tickets = [Ticket(x) for x in raw_other_tickets.strip("nearby tickets:\n").split("\n")]
+
+    return rules, my_ticket, other_tickets
+
+def test_value(value:int, condition:Tuple[int, ...]) -> bool:
+    return condition[0] <= value <= condition[1] or condition[2] <= value <= condition[3]
+
+def find_invalid(rules:List[Rule], tickets:List[Ticket]) -> Tuple[List[int], List[int]]:
+    # returns invalid values and indexes of invalid tickets
+
+    invalid_values = []
+    invalid_indexes = []
+
+    for i, ticket in enumerate(tickets):
+        for field in ticket.fields:
+            field_is_valid = False
+            for rule in rules:
+                if test_value(field, rule.ranges):
+                    field_is_valid = True
+            if not field_is_valid:
+                invalid_values.append(field)
+                invalid_indexes.append(i)
+
+    return invalid_values, invalid_indexes

16-ticketTranslation/python/partOne.py

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+from common import *
+
+
+def partOne(instr: str) -> int:
+    rules, _, tickets = parse(instr)
+    
+    invalid_values, _ = find_invalid(rules, tickets)
+
+    return sum(invalid_values)

16-ticketTranslation/python/partTwo.py

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+from common import *
+from pprint import pprint
+
+
+def partTwo(instr: str) -> int:
+    rules, my_ticket, tickets = parse(instr)
+
+    # purge bad indexes
+    _, invalid_indexes = find_invalid(rules, tickets)
+    invalid_indexes = list(reversed(sorted(invalid_indexes)))
+
+    for idx in invalid_indexes:
+        tickets.pop(idx)
+    
+    ticket_length = len(tickets[0].fields)
+    num_tickets = len(tickets)
+    num_rules = len(rules)
+
+    candidates = {rule.name: set() for rule in rules}
+
+    for col in range(ticket_length):
+        values = [ticket.fields[col] for ticket in tickets]
+
+        for rule_idx, rule in enumerate(rules):
+            complete_match = True
+            for v in values:
+                if not test_value(v, rule.ranges):
+                    complete_match = False
+                    break
+
+            if complete_match:
+                candidates[rule.name].add(col)
+
+    parameter_indexes = {}
+    removed = set()
+
+    product = 1
+
+    for col in range(ticket_length):
+        for name in candidates:
+            candidates_set = candidates[name] - removed
+
+            if len(candidates_set) == 1:
+                idx = candidates_set.pop()
+                parameter_indexes[name] = idx
+                removed.add(idx)
+
+    product = 1
+    for param in parameter_indexes:
+        if "departure" in param:
+            product *= my_ticket.fields[parameter_indexes[param]]
+
+    return product