107 lines
2.5 KiB
Python
107 lines
2.5 KiB
Python
import functools
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def parse(file):
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rules = []
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for line in file:
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line = line.strip()
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if line == "":
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break
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a, _, b = line.partition('|')
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rules.append((a,b))
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updates = []
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for line in file:
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line = line.strip()
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updates.append(line.split(','))
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return rules, updates
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def solve(file):
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rules, updates = parse(file)
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rules = set(rules)
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def isvalid(pages):
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for i in range(len(pages)):
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p = pages[i]
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for g in pages[i+1:]:
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if (g,p) in rules:
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return False
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return True
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t = 0
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invalid = []
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for pages in updates:
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if isvalid(pages):
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print(pages)
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t += int(pages[len(pages)//2])
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else:
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invalid.append(pages)
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print(t)
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t = 0
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for pages in invalid:
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rules2 = [(p,g) for p,g in rules if p in pages and g in pages]
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#print(pages, rules2)
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S = set(p for p,g in rules2)
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E = set(g for p,g in rules2)
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top = next(iter(S-E))
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# topological sort
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l = []
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seen = set()
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def visit(node):
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if node in seen: return
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seen.add(node)
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for p,g in rules2:
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if p == node and g not in seen:
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visit(g)
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l.append(node)
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visit(top)
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l.reverse()
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print(l)
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t += int(l[len(l)//2])
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print(t)
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# failed attempt: establish a total order by iterating the graph
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# to a fix point and then using it to sort the list.
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# failed because the graph is cyclic
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"""
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less = {p:set() for p,g in rules}
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for p,g in rules:
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less[p].add(g)
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print("less")
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for p in less:
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print(p,less[p])
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done = False
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while not done:
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done = True
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for p in less:
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for g in list(less[p]):
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if g in less:
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e = less[g] - less[p]
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if e:
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less[p] |= e
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done = False
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print("less2")
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for p in less:
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print(p,less[p])
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def compare(a,b):
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if a == b:
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return 0
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if a in less and b in less[a]:
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return -1
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return 1
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t = 0
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for pages in invalid:
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pages.sort(key = functools.cmp_to_key(compare))
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print(pages)
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assert(isvalid(pages))
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t += int(pages[len(pages)//2])
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print(t)
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"""
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solve(open("sample1.in"))
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solve(open("input"))
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