day 7 part 1 solution

Signed-off-by: Stephen Waits <swaits@amazon.com>

src/day07.rs

@@ -0,0 +1,71 @@
+// ==== day 7
+
+use crate::utils;
+use anyhow::Result;
+use std::{
+    collections::{HashMap, HashSet},
+    iter::{self, FromIterator},
+};
+
+// light red bags contain 1 bright white bag, 2 muted yellow bags.
+// dark orange bags contain 3 bright white bags, 4 muted yellow bags.
+// bright white bags contain 1 shiny gold bag.
+// muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
+// shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
+// dark olive bags contain 3 faded blue bags, 4 dotted black bags.
+// vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
+// faded blue bags contain no other bags.
+// dotted black bags contain no other bags.
+
+// parse data into a HashMap<&str, Vec<&str>>
+//
+// for example: "light red bags contain 1 bright white bag, 2 muted yellow bags."
+// becomes: { "light red": ["bright white", "muted yellow", "muted yellow"]}
+//
+fn parse(s: &str) -> HashMap<&str, Vec<&str>> {
+    s.lines()
+        .map(|l| {
+            let parsed: Vec<&str> = l.splitn(2, " bags contain ").collect();
+            let container = parsed[0];
+            let contents: Vec<&str> = match parsed[1].trim() {
+                "no other bags." => Vec::new(),
+                _ => parsed[1]
+                    .trim_end_matches('.')
+                    .split(',')
+                    .flat_map(|c| {
+                        let trimmed = c.trim_end_matches("bags").trim_end_matches("bag").trim();
+                        let count: usize = trimmed[0..1].parse().unwrap();
+                        let purse = &trimmed[2..];
+                        let seq: Vec<&str> = iter::repeat(purse).take(count).collect();
+                        seq
+                    })
+                    .collect(),
+            };
+            (container, contents)
+        })
+        .collect()
+}
+
+fn has_contents(data: &HashMap<&str, Vec<&str>>, container: &str, contents: &str) -> bool {
+    let these_contents: HashSet<&str> =
+        HashSet::from_iter(data.get(&container).unwrap().iter().cloned());
+    these_contents.contains(&contents)
+        || these_contents
+            .iter()
+            .any(|m| has_contents(data, m, contents))
+}
+
+pub fn run() -> Result<(usize, usize)> {
+    let data = utils::read_file("data/input-07.txt")?;
+    let answers = utils::read_i64s("data/output-07.txt")?;
+
+    let parsed = parse(&data);
+
+    let p1 = parsed
+        .keys()
+        .filter(|k| has_contents(&parsed, k, "shiny gold"))
+        .count();
+
+    assert_eq!(p1, answers[0] as usize);
+    Ok((p1, 0))
+}

src/main.rs

@@ -6,6 +6,7 @@ mod day03;
 mod day04;
 mod day05;
 mod day06;
+mod day07;
 mod utils;
 
 // TODO
@@ -25,5 +26,6 @@ fn main() -> Result<()> {
     println!("Day 04: {:?}", day04::run()?);
     println!("Day 05: {:?}", day05::run()?);
     println!("Day 06: {:?}", day06::run()?);
+    println!("Day 07: {:?}", day07::run()?);
     Ok(())
 }