day07.Rmd

---
title: "--- Day 7: Handy Haversacks ---"
author: Fleur Kelpin
date: Dec 7, 2020
output: github_document
---
```{r message=FALSE, warning=FALSE}
library(tidyverse)
input <- readr::read_lines("day07.txt") %>%
  as_tibble()
input
```
# Part 1
How many bag colors can eventually contain at least one shiny gold bag? 
```{r}
who_contains <- function(type) {
  input %>%
    extract(value,
      paste0("(.+) bags contain .*", type, " bags?"),
      into = c("container")
    ) %>%
    drop_na() %>%
    {
      .$container
    }
}
who_contains("shiny gold")
```
```{r}
all_contains <- function(containers, checked) {
  new_containers <- containers %>%
    map(who_contains) %>%
    unlist() %>%
    unique() %>%
    setdiff(checked)
  num_found <- length(new_containers)
  if (num_found == 0) {
    return(0)
  }
  length(new_containers) + all_contains(
    new_containers,
    unique(c(
      checked,
      containers,
      new_containers
    ))
  )
}
all_contains("shiny gold", c())
```
# Part 2
How many individual bags are required inside your single shiny gold bag?
```{r}
contents <- function(type) {
  inside <- input %>%
    extract(value, paste0(type, " bags contain (.*)"), into = "line") %>%
    separate_rows(line, sep = ",") %>%
    extract(line,
      "(\\d+) (.*) bags?",
      convert = TRUE, into = c("num", "type")
    ) %>%
    drop_na()
  if (nrow(inside) == 0) {
    return(0)
  }
  inside %>%
    rowwise() %>%
    mutate(total = num + num * contents(type)) %>%
    {
      sum(.$total)
    }
}

contents("shiny gold")
```