advent_of_code_2021

commit 605b631b1e31767e3772224d11f14bb18c91aedd
parent 0b23461c5d9d68fc0084956f2eb70b31822ca1c1
Author: Eamon Caddigan <eamon.caddigan@gmail.com>
Date:   Fri, 10 Dec 2021 08:33:39 -0500

Soution to day 10, part 1

Diffstat:
A
day10_part1.py
 | 
66
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 66 insertions(+), 0 deletions(-)
diff --git a/day10_part1.py b/day10_part1.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+"""Advent of Code 2021, day 10 (part 1): Syntax Scoring
+For part 1, we are finding 'corrupted' lines from the navigation subsystem
+(ones that have mismatched brackets) and scoring them."""
+
+# I'm not going to bother trying to use pandas for this one.
+
+from utils import get_puzzle_input
+
+EXAMPLE_INPUT = \
+"""[({(<(())[]>[[{[]{<()<>>
+[(()[<>])]({[<{<<[]>>(
+{([(<{}[<>[]}>{[]{[(<()>
+(((({<>}<{<{<>}{[]{[]{}
+[[<[([]))<([[{}[[()]]]
+[{[{({}]{}}([{[{{{}}([]
+{<[[]]>}<{[{[{[]{()[[[]
+[<(<(<(<{}))><([]([]()
+<{([([[(<>()){}]>(<<{{
+<{([{{}}[<[[[<>{}]]]>[]]
+"""
+
+def convert_input_to_list(input_string):
+    """Convert the puzzle input to a list of strings"""
+    return input_string.rstrip('\n').split('\n')
+
+def is_open_bracket(bracket):
+    """Returns True iff the character is an open bracket"""
+    return bracket in '([{<'
+
+def match_bracket(bracket):
+    """Given an open bracket, return the matching close bracket"""
+    return {'(': ')', '[': ']', '{': '}', '<': '>'}[bracket]
+
+def score_bracket(bracket):
+    """Given a close bracket, return its associated score"""
+    return {')': 3, ']': 57, '}': 1197, '>': 25137}[bracket]
+
+def score_line(line):
+    """Return the 'score' of a corrupted line, or 0 for lines that are not
+    corrupt"""
+    # Going with a straightforward solution here: using a stack, pushing open
+    # brackets and popping when we find close brackets. If we have the wrong
+    # close bracket, return a score for the bracket we have, otherwise we
+    # return 0.
+    bracket_stack = []
+    for bracket in line:
+        if is_open_bracket(bracket):
+            bracket_stack.append(bracket)
+        else:
+            if match_bracket(bracket_stack.pop()) != bracket:
+                return score_bracket(bracket)
+    return 0
+
+def solve_puzzle(input_string):
+    """Return the numeric solution to the puzzle"""
+    return sum([score_line(l) for l in convert_input_to_list(input_string)])
+
+def main():
+    """Run when the file is called as a script"""
+    assert solve_puzzle(EXAMPLE_INPUT) == 26397
+    print("Score for corrupted lines:",
+          solve_puzzle(get_puzzle_input(10)))
+
+if __name__ == "__main__":
+    main()