2021 Day 13

Author

Nathan Moore

— Day 13: Transparent Origami —

Congratulations on your purchase! To activate this infrared thermal imaging camera system, please enter the code found on page 1 of the manual.

The manual is transparent paper with dots and folding instructions.

How many dots are visible after completing just the first fold instruction on your transparent paper?

library(tidyverse)

my_file <- here::here("2021", "data-2021-13.txt")
x <- readLines(my_file)

Maybe write an explanation of the solution approach here

inputs <- tibble(inpt = x) %>%
    separate(inpt, c("X", "Y"), sep = ",", convert = TRUE)

Warning: Expected 2 pieces. Missing pieces filled with `NA` in 13 rows [847, 848, 849,
850, 851, 852, 853, 854, 855, 856, 857, 858, 859].

folds = inputs %>%
    filter(is.na(Y) & X != '') %>%
    select(-Y) %>%
    separate(X, c("dir", "num"), sep = "=", convert = TRUE) %>%
    mutate(dir = str_remove(dir, "fold along "))

thermal = inputs %>%
    filter(!is.na(Y)) %>%
    mutate(X = as.numeric(X))

for (j in seq_along(folds)) {
    if (folds$dir[[j]] == "x") {
        for (k in seq_along(thermal$X)) {
            if (thermal$X[[k]] > folds$num[[j]]){
                thermal$X[[k]] = folds$num[[j]] - (thermal$X[[k]] - folds$num[[j]])
            }
        }
    } else {
        for (k in seq_along(thermal$Y)) {
            if (thermal$Y[[k]] > folds$num[[j]]){
                thermal$Y[[k]] = folds$num[[j]] - (thermal$Y[[k]] - folds$num[[j]])
            }
        }
    }
    break
}

nrow(thermal %>% distinct())

[1] 684

— Part Two —

Finish folding the transparent paper according to the instructions. The manual says the code is always eight capital letters.

What code do you use to activate the infrared thermal imaging camera system?

inputs <- tibble(inpt = x) %>%
    separate(inpt, c("X", "Y"), sep = ",", convert = TRUE)

Warning: Expected 2 pieces. Missing pieces filled with `NA` in 13 rows [847, 848, 849,
850, 851, 852, 853, 854, 855, 856, 857, 858, 859].

folds = inputs %>%
    filter(is.na(Y) & X != '') %>%
    select(-Y) %>%
    separate(X, c("dir", "num"), sep = "=", convert = TRUE) %>%
    mutate(dir = str_remove(dir, "fold along "))

thermal = inputs %>%
    filter(!is.na(Y)) %>%
    mutate(X = as.numeric(X))

for (j in seq_along(folds$dir)) {
    if (folds$dir[[j]] == "x") {
        for (k in seq_along(thermal$X)) {
            if (thermal$X[[k]] > folds$num[[j]]){
                thermal$X[[k]] = folds$num[[j]] - (thermal$X[[k]] - folds$num[[j]])
            }
        }
    } else {
        for (k in seq_along(thermal$Y)) {
            if (thermal$Y[[k]] > folds$num[[j]]){
                thermal$Y[[k]] = folds$num[[j]] - (thermal$Y[[k]] - folds$num[[j]])
            }
        }
    }
}

arr = array(".", c(max(thermal$Y)+1, max(thermal$X)+1))

for (k in seq_along(thermal$X)) {
    arr[thermal$Y[[k]]+1, thermal$X[[k]]+1] = '#'
}

for (a in 1:6) { 
    print(paste(arr[a,], collapse=""))
}

[1] "..##.###..####.###..#.....##..#..#.#..#"
[1] "...#.#..#....#.#..#.#....#..#.#.#..#..#"
[1] "...#.#..#...#..###..#....#....##...####"
[1] "...#.###...#...#..#.#....#.##.#.#..#..#"
[1] "#..#.#.#..#....#..#.#....#..#.#.#..#..#"
[1] ".##..#..#.####.###..####..###.#..#.#..#"