adventofcode2024/day05-1.py

# The first section specifies the page ordering rules, one per line. 
# The first rule, 47|53, means that if an update includes both 
# page number 47 and page number 53, then page number 47 must be 
# printed at some point before page number 53. (47 doesn't necessarily 
# need to be immediately before 53; other pages are allowed to be 
# between them.)

# The second section specifies the page numbers of each update. 
# Because most safety manuals are different, the pages needed in the 
# updates are different too. The first update, 75,47,61,53,29, means 
# that the update consists of page numbers 75, 47, 61, 53, and 29.

def main051():
    with open("./input05.txt", "r", encoding="utf-8") as f:
        lines = [l.strip() for l in f.readlines()]
    
    rules = []
    updates = []
    for i, line in enumerate(lines):
        if "|" not in line:
            first_update = i + 1
            break
        rules.append([int(x) for x in line.split("|")])
    for i, line in enumerate(lines[first_update:]):
        updates.append([int(x) for x in line.split(",")])
    
    valid_updates = []
    total_vu = 0
    for u in updates:
        relevant_rules = [r for r in rules if all([x in u for x in r])]
        if all([u.index(rule[0]) < u.index(rule[1]) for rule in relevant_rules]):
            valid_updates.append(u)
            total_vu += u[(len(u)-1)//2]

    print(total_vu)

    



if __name__ == "__main__":
    main051()