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diff --git a/day5/day5.readme b/day5/day5.readme new file mode 100644 index 0000000..611dc87 --- /dev/null +++ b/day5/day5.readme @@ -0,0 +1,37 @@ +--- Day 5: Doesn't He Have Intern-Elves For This? --- + +Santa needs help figuring out which strings in his text file are naughty or nice. + +A nice string is one with all of the following properties: + + - It contains at least three vowels (aeiou only), like aei, xazegov, or aeiouaeiouaeiou. + - It contains at least one letter that appears twice in a row, like xx, abcdde (dd), or aabbccdd (aa, bb, cc, or dd). + - It does not contain the strings ab, cd, pq, or xy, even if they are part of one of the other requirements. + +For example: + + - ugknbfddgicrmopn is nice because it has at least three vowels (u...i...o...), a double letter (...dd...), and none of the disallowed substrings. + - aaa is nice because it has at least three vowels and a double letter, even though the letters used by different rules overlap. + - jchzalrnumimnmhp is naughty because it has no double letter. + - haegwjzuvuyypxyu is naughty because it contains the string xy. + - dvszwmarrgswjxmb is naughty because it contains only one vowel. + +How many strings are nice? + +--- Part Two --- + +Realizing the error of his ways, Santa has switched to a better model of determining whether a string is naughty or nice. None of the old rules apply, as they are all clearly ridiculous. + +Now, a nice string is one with all of the following properties: + + - It contains a pair of any two letters that appears at least twice in the string without overlapping, like xyxy (xy) or aabcdefgaa (aa), but not like aaa (aa, but it overlaps). + - It contains at least one letter which repeats with exactly one letter between them, like xyx, abcdefeghi (efe), or even aaa. + +For example: + + - qjhvhtzxzqqjkmpb is nice because is has a pair that appears twice (qj) and a letter that repeats with exactly one letter between them (zxz). + - xxyxx is nice because it has a pair that appears twice and a letter that repeats with one between, even though the letters used by each rule overlap. + - uurcxstgmygtbstg is naughty because it has a pair (tg) but no repeat with a single letter between them. + - ieodomkazucvgmuy is naughty because it has a repeating letter with one between (odo), but no pair that appears twice. + +How many strings are nice under these new rules? |