91 lines
2.5 KiB
Python
91 lines
2.5 KiB
Python
#!/usr/bin/env python3
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import re
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def yield_spans(gs: dict):
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for g in gs.values():
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yield g[:2]
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yield g[2:]
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def in_spans(x, spans):
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for span in spans:
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if span[0] <= x <= span[1]:
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return True
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return False
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lines = (x.strip() for x in open("input.txt"))
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REGEX_RANGES = re.compile(r"^([a-z ]+): (\d+)-(\d+) or (\d+)-(\d+)$")
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groups = {}
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your = ()
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nearby = []
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read_step = 0
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group_keys = []
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group_cols = []
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for line in lines:
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if read_step == 0:
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if line == "":
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read_step = 1
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continue
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match = REGEX_RANGES.match(line)
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groups[match[1]] = list(map(int, match.groups()[1:]))
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elif read_step == 1:
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if line == "":
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read_step = 2
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continue
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if line.startswith("your"):
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continue
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your = list(map(int, line.split(',')))
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elif read_step == 2:
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if line.startswith("nearby"):
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continue
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nearby.append(list(map(int, line.split(','))))
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group_keys = list(groups.keys())
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group_cols = [-1]*len(group_keys)
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valid_spans = []
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for span in yield_spans(groups):
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start_idx = next((i for i, v in enumerate(valid_spans) if span[0] <= v[1]), len(valid_spans))
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end_idx = next((len(valid_spans)-i for i, v in enumerate(valid_spans[::-1]) if span[1] >= v[0]), 0)
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for idx in range(start_idx, end_idx):
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popped = valid_spans.pop(start_idx)
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span = (min(popped[0], span[0]), max(popped[1], span[1]))
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valid_spans.insert(start_idx, tuple(span))
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print("Valid Spans:", valid_spans)
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valid_tickets = filter(lambda n: not any(True for x in n if not in_spans(x, valid_spans)), nearby)
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cnt_grp = len(groups)
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classes = [2**cnt_grp - 1] * len(your)
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for ticket in valid_tickets:
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for ig, key in enumerate(group_keys):
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spans = groups[key]
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spans = tuple(zip(spans[::2], spans[1::2]))
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for it, t in enumerate(ticket):
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if not in_spans(t, spans):
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classes[it] &= ~(2**ig)
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print("Possible Columns:", list(map(lambda x: format(x, '0'+str(cnt_grp)+'b')[::-1], classes)))
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fixed = 0
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for _ in range(len(your)):
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col, power_two = next(((i, v) for i, v in enumerate(classes) if not (v & (v-1)) and v > 0))
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pos = power_two.bit_length()-1
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fixed |= power_two
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classes = list(map(lambda x: x & ~fixed, classes))
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group_cols[pos] = col
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print("Mapping:", dict(zip(group_keys, group_cols)))
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result = 1
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for name, col in zip(group_keys, group_cols):
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if name.startswith("departure"):
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result *= your[col]
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print(result)
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