Solution: Day 5 - part 1 & 2

Author: Kaba8081

2024/5/main.py

@@ -0,0 +1,101 @@
+# 'Advent of code' solution for year 2024 day 5
+import os
+import sys
+                        
+global DIR_PATH
+DIR_PATH = os.path.dirname(os.path.realpath(__file__))
+
+def isUpdateCorrect(page_ordering: list[(int, int)], update: list[int]) -> tuple[bool, list[int]]:
+    """Check if the given update is correct
+    :param page_ordering: list of dependencies
+    :param update: list of pages
+    :return: True if the update is correct, False otherwise,
+    :return: list of pages in correct order
+    """
+    _dependencies = {} # page -> dependencies
+    _print_order = []
+    fixed_update = update.copy()
+    isCorrect = True
+
+    for dependency in page_ordering:
+        # both pages need to be in the update
+        if not dependency[0] in update or not dependency[1] in update:
+            continue
+        if dependency[1] not in _dependencies:
+            _dependencies[dependency[1]] = [dependency[0]]
+        elif dependency[0] not in _dependencies[dependency[1]]:
+            _dependencies[dependency[1]].append(dependency[0])
+
+    for page in update:
+        # page has no dependencies
+        if not page in _dependencies.keys():
+            _print_order.append(page)
+            continue
+
+        # page was rendered before all dependencies
+        for dependency in _dependencies[page]:
+            if dependency not in _print_order:
+                isCorrect = False
+                fixed_update.remove(page)
+                fixed_update.insert(fixed_update.index(dependency) + 1, page)
+
+        _print_order.append(page)
+        
+    return isCorrect, fixed_update
+
+def part1(page_ordering: list[(int, int)], updates: list[(int, int)]) -> int:
+    """Find all correct udpates and sum the middle pages"""
+    page_sum = 0
+
+    for update in updates:
+        if isUpdateCorrect(page_ordering, update)[0]:
+            _len = len(update)
+            page_sum += update[_len // 2]
+
+    return page_sum
+
+def part2(page_ordering: list[(int, int)], updates: list[(int, int)]) -> int:
+    """Correct invalid udpates and sum the middle pages"""
+    page_sum = 0
+
+
+    for update in updates:
+        correct, fixed = isUpdateCorrect(page_ordering, update)
+        if correct:
+            continue
+
+        while not correct:
+            correct, fixed = isUpdateCorrect(page_ordering, fixed)
+        _len = len(fixed)
+        page_sum += fixed[_len // 2]
+
+    return page_sum
+
+def get_input():
+    input = None
+    if os.path.isfile(os.path.join(DIR_PATH, "input.txt")):
+        with open(os.path.join(DIR_PATH, "input.txt"), "r") as file:    
+            input = file.read().strip().split("\n\n")
+        return input
+    else:
+        print("Error! Input file does not exist!")
+        sys.exit()
+                        
+if __name__ == "__main__":
+    input = get_input()
+    if not input:
+        print("Error! Input file is empty!")
+        sys.exit()
+
+    # parse input
+    page_ordering = input[0].split("\n")
+    page_ordering = [[int(num) for num in dependeny.split("|")] for dependeny in page_ordering]
+    updates = input[1].split("\n")
+    updates = [[int(num) for num in update.split(",")] for update in updates]
+      
+    result1 = part1(page_ordering, updates)
+    print(f"Part 1: {result1}")
+    result2 = part2(page_ordering, updates)
+    print(f"Part 2: {result2}")
+    
+    sys.exit()