import ./common, std/[strutils, sequtils, strformat, sugar, sets, math] proc parseLine(s: string): seq[seq[string]] = s.split(" | ").mapIt(it.split(" ")) proc p1(c: seq[string]): int = c.reduce((a: int, l: string) => a + l.parseLine()[1].reduce((b: int, h) => b + int(h.len() in [2, 3, 4, 7]), 0), 0) proc numShared(s1: string, s2: string): int = (s1.toHashSet() * s2.toHashSet()).len() proc p2(c: seq[string]): int = for oLine in c.map(parseLine): let four = oLine[0].findFirst((s) => s.len() == 4) let seven = oLine[0].findFirst((s) => s.len() == 3) for i, output in oLine[1].pairs(): let outputVal = case output.len(): of 2: 1 of 3: 7 of 4: 4 of 7: 8 of 5: case output.numShared(four) + output.numShared(seven): of 4: 2 of 6: 3 else: 5 else: case output.numShared(four) + output.numShared(seven): of 6: 0 of 5: 6 else: 9 let x = (abs(oLine[1].len() - i) - 1) result += outputVal * int(10 ^ x) # Explanation: # 1, 7, 8, and 4 are known and may be identified just by length, so we only # need to figure out the 5- and 6- inputs, 0, 2, 3, 5, 6, and 9 # we should be able to do this by seeing how many segments are shared with the # known digits # 5-inputs: 235 # 2: shares 2 with 4, 1 with 1, 2 with 7 # 3: shares 3 with 4, 2 with 1, 3 with 7 # 5: shares 3 with 4, 1 with 1, 2 with 7 # 6-inputs: 069 # 0: shares 3 with 4, 2 with 1, 3 with 7 # 6: shares 3 with 4, 1 with 1, 2 with 7 # 9: shares 4 with 4, 2 with 1, 3 with 7 # from this information, we can identify each digit simply by knowing the # number of shared segments with 4 and 7 alone: # 2: 22 # 3: 33 # 5: 32 # 0: 33 # 6: 32 # 9: 43 doDay(8, (n) => n.loadInput(), p1, p2, """be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce""".split('\n'), 26, 61229)