advent_of_code_2025

My (attempted) solutions to the 2025 Advent of Code
git clone https://git.eamoncaddigan.net/advent_of_code_2025.git
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day06.R (1844B)

      1 #!/usr/bin/env Rscript
      2 
      3 source("src/utils.R")
      4 
      5 test_input <- c(
      6   "123 328  51 64 ",
      7   " 45 64  387 23 ",
      8   "  6 98  215 314",
      9   "*   +   *   +  "
     10 )
     11 puzzle_input <- aoc_input(6)
     12 
     13 parse_input <- function(input_lines) {
     14   split_lines <- strsplit(trimws(input_lines), "\\s+")
     15   list(
     16     numbers = split_lines[1:(length(split_lines) - 1)] |>
     17       unlist() |>
     18       as.numeric() |>
     19       matrix(nrow = length(split_lines) - 1, byrow = TRUE),
     20     operators = split_lines[[length(split_lines)]]
     21   )
     22 }
     23 
     24 solve_problems <- function(numbers, operators) {
     25   sum(c(
     26     apply(numbers[, operators == "+"], 2, sum),
     27     apply(numbers[, operators == "*"], 2, prod)
     28   ))
     29 }
     30 
     31 part1 <- function(input_lines) {
     32   input_parsed <- parse_input(input_lines)
     33   solve_problems(
     34     input_parsed$numbers,
     35     input_parsed$operators
     36   )
     37 }
     38 
     39 test_part1 <- function() {
     40   stopifnot(part1(test_input) == 4277556)
     41 }
     42 
     43 
     44 parse_part2 <- function(input_lines) {
     45   char_mat <- input_lines |>
     46     strsplit("", fixed = TRUE) |>
     47     (\(x) matrix(unlist(x), ncol = length(x), byrow = FALSE))()
     48   is_separator <- apply(char_mat == " ", 1, all)
     49   list(
     50     numbers = char_mat[!is_separator, 1:(ncol(char_mat) - 1)] |>
     51       apply(1, \(x) paste(x, collapse = "")) |>
     52       as.numeric() |>
     53       split(cumsum(is_separator)[!is_separator]),
     54     operators = char_mat[char_mat[, ncol(char_mat)] != " ", ncol(char_mat)]
     55   )
     56 }
     57 
     58 part2 <- function(input_lines) {
     59   input_parsed <- parse_part2(input_lines)
     60   mapply(
     61     \(x, y) if (y == "+") sum(x) else prod(x),
     62     input_parsed$numbers,
     63     input_parsed$operators
     64   ) |>
     65     sum()
     66 }
     67 
     68 test_part2 <- function() {
     69   stopifnot(part2(test_input) == 3263827)
     70 }
     71 
     72 main <- function() {
     73   test_part1()
     74   cat(sprintf("Part 1 solution: %0.0f\n", part1(puzzle_input)))
     75   test_part2()
     76   cat(sprintf("Part 2 solution: %0.0f\n", part2(puzzle_input)))
     77 }
     78 
     79 main()