Solving Advent of Code 2020-04 with R.
[Disclaimer] Obviously, this post contains a big spoiler about Advent of Code.
Instructions
Step 1
- Inputs are of the form of
ecl:gry pid:860033327 eyr:2020 hcl:#fffffd byr:1937 iyr:2017 cid:147 hgt:183cm iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884 hcl:#cfa07d byr:1929 hcl:#ae17e1 iyr:2013 eyr:2024 ecl:brn pid:760753108 byr:1931 hgt:179cm hcl:#cfa07d eyr:2025 pid:166559648 iyr:2011 ecl:brn hgt:59in Where each “passport” is separated by a new line.
To be considered valid, a passport has to have all ofc("byr","iyr","eyr", "hgt", "hcl", "ecl", "pid").
Step 2
To be considered valid, a passport has to have all ofc("byr","iyr","eyr", "hgt", "hcl", "ecl", "pid"), plus, each entry has to validate a series of rules.
Find the complete instructions at:https://adventofcode.com/2020/day/4.
R solution
Part one
library(magrittr) # Read the data ipt <- readLines("2020-04-aoc.txt" ) %>% # pasting everything into one big character string paste(collapse = "\n") %>% # splitting where there are two \n\n (new lines) strsplit("\n\n") %>% .[[1]] %>% # Removing the new lines gsub("\n", " ", .) library(purrr, warn.conflicts = FALSE) is_north_pole_valid <- function( x, patt = c("byr","iyr","eyr", "hgt", "hcl", "ecl", "pid") ){ map_lgl( patt, ~ grepl(.x, x) ) %>% all() } map_dbl( ipt, ~{ if (is_north_pole_valid(.x)) return(1) return(0) } ) %>% sum() ## [1] 204 Part two
ipt %>% # Remove the unvalid passport discard(~ !is_north_pole_valid(.x)) %>% # Split stuff strsplit(" ") %>% map_dbl(~{ # Now, the heavy lifting # we have a string of key:value pairs, # split it vals <- map_chr(.x, ~ gsub("([^:]*):(.*)", "\\2", .x)) names(vals) <- map_chr(.x, ~ gsub("([^:]*):(.*)", "\\1", .x)) # checking that values are inside range if (! dplyr::between(vals["byr"], 1920, 2002) ) return(0) if (! dplyr::between(vals["iyr"], 2010, 2020) ) return(0) if (! dplyr::between(vals["eyr"], 2020, 2030) ) return(0) # If height is in inch, check the range if ( grepl("in", vals["hgt"]) ) { if (! dplyr::between(gsub("in", "", vals["hgt"]), 59, 76)) return(0) } else if (grepl("cm", vals["hgt"])) { if (! dplyr::between(gsub("cm", "", vals["hgt"]), 150, 193)) return(0) } else { # No unit provided return(0) } if (! grepl("^#[a-f0-9]{6}$", vals["hcl"])) return(0) if (! vals["ecl"] %in% c("amb","blu", "brn", "gry", "grn","hzl", "oth")) return(0) if (! grepl("^[0-9]{9}$", vals["pid"])) return(0) return(1) } ) %>% sum() ## [1] 179 
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