A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Advent of Code: solutions & explanationsAfter 2503 seconds, what is the maximum distance any reindeer has flown?After 50 iterations?Alternate approach: complex numbersAlternate approach: numerical conversionAlternate approaches: for/first or for/oraoc-racketaoc-racket/day01aoc-racket/day02aoc-racket/day03aoc-racket/day04aoc-racket/day05aoc-racket/day06aoc-racket/day07aoc-racket/day08aoc-racket/day09aoc-racket/day10aoc-racket/day11aoc-racket/day12aoc-racket/day13aoc-racket/day14aoc-racket/day15aoc-racket/day16aoc-racket/day17aoc-racket/day18aoc-racket/day19aoc-racket/day20aoc-racket/day21aoc-racket/day22aoc-racket/day23aoc-racket/day24aoc-racket/day25apply, in Day 2 / How much paper is needed to wrap the boxes?assoc, in Day 16 / Which Sue matches the attribute input, with the “retroencabulator” rules?At what point does the elevator enter the basement?case, in Day 16 / Which Sue matches the attribute input, with the “retroencabulator” rules?compile-enforce-module-constants, in Day 7 / What’s the signal on wire a if wire b is overridden with a’s original value?cond, in Day 7 / What’s the signal on wire a?Day 1Day 10Day 11Day 12Day 13Day 14Day 15Day 16Day 17Day 18Day 19Day 2Day 20Day 21Day 22Day 23Day 24Day 25Day 3Day 4Day 5Day 6Day 7Day 8Day 9define-syntax, in Day 7 / What’s the signal on wire a?define-syntax, in Day 14 / After 2503 seconds, what is the maximum distance any reindeer has flown?divisors, in Day 20 / What’s the first house that gets the target number of presents?filter, in Day 20 / What’s the first house that gets the target number of presents, if each elf delivers 11 gifts to 50 houses?flatten, in Day 12 / What’s the sum of all the numbers in the document?for*/first, in Day 24 / What’s the score of the optimal group of packages, when divided into three groups?for/first, in Day 1 / Alternate approaches: for/first or for/orfor/fold, in Day 1 / At what point does the elevator enter the basement?for/fold, in Day 10 / What’s the length of the sequence after 40 iterations?for/fold, in Day 14 / Under the new rule, how many points does the winning reindeer have?for/fold, in Day 18 / How many lights are on after 100 iterations of the light-switching rules?for/fold, in Day 21 / What’s the least we can spend and win?for/or, in Day 1 / Alternate approaches: for/first or for/orfrequency-hash, in Day 14 / Under the new rule, how many points does the winning reindeer have?Hard ModeHow about six zeroes?How many combinations have the minimum number of containers?How many combinations of containers fit exactly 150 liters?How many distinct molecules can be created after one transformation?How many grid cells are visited if the path is split?How many grid cells are visited?How many lights are lit after following the instructions?How many lights are on after 100 iterations of the light-switching rules?How many lights are on after 100 iterations, if the corner bulbs are always lit?How many strings are “nice” under new rules?How many strings are “nice”?How much paper is needed to wrap the boxes?How much ribbon is needed to wrap the boxes?if, in Day 7 / What’s the signal on wire a?in-permutations, in Day 9 / What’s the shortest route that visits all the cities?in-permutations, in Day 13 / What’s the optimal happiness score for a seating arrangement of eight?in-permutations, in Day 13 / Optimizing in-permutationsjsexpr?, in Day 12 / What’s the sum of all the numbers in the document?last, in Day 15 / What’s the best cookie we can make with 100 tsps that’s exactly 500 calories?let, in Day 7 / What’s the signal on wire a?map, in Day 14 / After 2503 seconds, what is the maximum distance any reindeer has flown?map, in Day 2 / How much paper is needed to wrap the boxes?map, in Day 3 / How many grid cells are visited?max, in Day 9 / What’s the longest route?max, in Day 14 / After 2503 seconds, what is the maximum distance any reindeer has flown?md5, in Day 4 / What is the lowest-numbered MD5 hash starting with five zeroes?min, in Day 9 / What’s the shortest route that visits all the cities?Optimizing in-permutationspregexp, in Day 5 / How many strings are “nice”?read, in Day 8 / What’s the difference between the literal length of the strings, and their length in memory?read, in Day 16 / Which Sue matches the attribute input, with the “retroencabulator” rules?read-json, in Day 12 / What’s the sum of all the numbers in the document?Refactored solutionregexp-match, in Day 11 / What’s the next password that meets the criteria?regexp-match, in Day 5 / How many strings are “nice”?regexp-match*, in Day 1 / Where does the elevator land?regexp-match*, in Day 10 / What’s the length of the sequence after 40 iterations?regexp-match-positions*, in Day 19 / How many distinct molecules can be created after one transformation?regexp-replace*, in Day 11 / What’s the next password that meets the criteria?regexp-replace*, in Day 19 / How many distinct molecules can be created after one transformation?remove-duplicates, in Day 19 / How many distinct molecules can be created after one transformation?shuffle, in Day 19 / What’s the fewest number of transformations that will generate the test module?sort, in Day 24 / What’s the score of the optimal group of packages, when divided into three groups?string-length, in Day 8 / What’s the difference between the literal length of the strings, and their length in memory?Testing Day 1Testing Day 10Testing Day 11Testing Day 12Testing Day 13Testing Day 14Testing Day 15Testing Day 16Testing Day 17Testing Day 18Testing Day 19Testing Day 2Testing Day 20Testing Day 21Testing Day 22Testing Day 23Testing Day 24Testing Day 25Testing Day 3Testing Day 4Testing Day 5Testing Day 6Testing Day 7Testing Day 8Testing Day 9thunk*, in Day 23 / What’s the value in register b after the program runs?Under the new rule, how many points does the winning reindeer have?vector, in Day 6 / How many lights are lit after following the instructions?What code do you give the machine?What is the lowest-numbered MD5 hash starting with five zeroes?What is the total brightness of the lights if the rules are reinterpreted?What’s the best cookie we can make with 100 tsps of ingredients?What’s the best cookie we can make with 100 tsps that’s exactly 500 calories?What’s the difference between the literal length of the strings, and their length in memory?What’s the difference between the re-encoded length of the literal string, and the original length?What’s the fewest number of transformations that will generate the test module?What’s the first house that gets the target number of presents, if each elf delivers 11 gifts to 50 houses?What’s the first house that gets the target number of presents?What’s the least (mana) we can spend and win?What’s the least we can spend and win?What’s the length of the sequence after 40 iterations?What’s the longest route?What’s the most we can spend and lose?What’s the next password that meets the criteria?What’s the next valid password after that?What’s the optimal happiness score for a seating arrangement of eight?What’s the optimal happiness score, including ourself in the seating?What’s the optimal score when divided into four groups?What’s the score of the optimal group of packages, when divided into three groups?What’s the shortest route that visits all the cities?What’s the signal on wire a if wire b is overridden with a’s original value?What’s the signal on wire a?What’s the sum of all the numbers in the document?What’s the sum of all the numbers, if hash tables with value "red" are ignored?What’s the value in register b after the program runs?What’s the value in register b if register a starts as 1?Where does the elevator land?Which Sue matches the attribute input, with the “retroencabulator” rules?Which Sue matches the attribute input?You’re a Wizard, Henry~v, in Day 8 / What’s the difference between the re-encoded length of the literal string, and the original length?