Day 1: Not Quite Lisp

Reference

library(tidyverse)

input <- read_lines(file = "inputs/2015/01.txt")

Part One

Solution

moves <- tibble(
    input = str_split_1(input, ""),
    move = case_match(input, "(" ~  1L, ")" ~ -1L),
    height = cumsum(move)
)

cat("Final floor:", tail(moves$height, 1), "\n")
## Final floor: 232

Full Table

Part Two

Solution

basement_entry_position <- moves |> 
    rowid_to_column("time") |> 
    filter(height == -1) |> 
    slice(1) |> 
    pull(time)

cat("Basement position:", basement_entry_position, "\n")
## Basement position: 1783

Full Table

Plot

moves_plot <- moves |> rowid_to_column("time")
final_floor <- tail(moves$height, 1)

moves_plot |> 
    ggplot(aes(x = time, y = height)) +
    geom_line() +
    geom_hline(yintercept = 0, linetype = "dashed", color = "gray50", alpha = 0.5) +
    geom_point(data = moves_plot |> filter(time == basement_entry_position),
               color = "red", size = 3) +
    geom_point(data = moves_plot |> filter(time == max(time)),
               color = "blue", size = 3) +
    annotate("label", x = max(moves_plot$time) - 650, y = final_floor - 25,
             label = paste("Part 1:\nFloor", final_floor),
             color = "blue", fill = "white", alpha = 0.8) +
    annotate("label", x = basement_entry_position + 500, y = 150, 
             label = paste("Part 2:\nStep", basement_entry_position),
             vjust = 1.5, color = "red", fill = "white", alpha = 0.8) +
    labs(x = "Step", y = "Floor") +
    theme_bw()