1 files changed, 88 insertions, 0 deletions
diff --git a/src/bin/day16.rs b/src/bin/day16.rs
new file mode 100644
index 0000000..48295ce
--- /dev/null
+++ b/src/bin/day16.rs
@@ -0,0 +1,88 @@
+use std::collections::HashMap;
+use regex::Regex;
+
+fn main() {
+    let input = advent::read_lines(16);
+    let search = HashMap::from([
+        ("children", 3),
+        ("cats", 7),
+        ("samoyeds", 2),
+        ("pomeranians", 3),
+        ("akitas", 0),
+        ("vizslas", 0),
+        ("goldfish", 5),
+        ("trees", 3),
+        ("cars", 2),
+        ("perfumes", 1),
+    ]);
+    println!("16a: {}", find_aunt(&input, &search, false));
+    println!("16b: {}", find_aunt(&input, &search, true));
+}
+
+struct Aunt {
+    name: u16,
+    attributes: HashMap<String, u8>,
+}
+
+impl Aunt {
+    fn new(input: &str) -> Aunt {
+        let re = Regex::new(r"([a-z]+): ([0-9]+)").unwrap();
+        let re_aunt = Regex::new(r"^Sue ([0-9]+):").unwrap();
+
+        let name = re_aunt.captures(input).unwrap()[1].parse::<u16>().unwrap();
+
+        let mut aunt = Aunt {
+            name,
+            attributes: HashMap::new(),
+        };
+
+        for cap in re.captures_iter(input) {
+            let attribute = cap[1].to_string();
+            let amount = cap[2].parse::<u8>().unwrap();
+            aunt.attributes.insert(attribute, amount);
+        }
+
+        aunt
+    }
+
+    fn has_attributes(&self, attributes: &HashMap<&str, u8>, outdated: bool) -> bool {
+        if outdated {
+            self.has_attributes_v2(attributes)
+        } else {
+            self.has_attributes_v1(attributes)
+        }
+    }
+
+    fn has_attributes_v1(&self, attributes: &HashMap<&str, u8>) -> bool {
+        for (attr, val) in attributes {
+            if let Some(myval) = self.attributes.get(*attr) {
+                if myval != val {
+                    /* found non-matching attribute */
+                    return false;
+                }
+            }
+        }
+        true
+    }
+
+    fn has_attributes_v2(&self, attributes: &HashMap<&str, u8>) -> bool {
+        for (attr, val) in attributes {
+            if let Some(myval) = self.attributes.get(*attr) {
+                match attr {
+                    x if ["cats", "trees"].contains(x) => if myval <= val { return false; },
+                    x if ["pomeranians", "goldfish"].contains(x) => if myval >= val { return false; },
+                    _ => if myval != val { return false; }
+                }
+            }
+        }
+        true
+    }
+}
+
+fn find_aunt(input: &[String], search: &HashMap<&str, u8>, outdated: bool) -> u16 {
+    input.iter()
+         .map(|x| Aunt::new(x))
+         .find(|x| x.has_attributes(search, outdated))
+         .unwrap()
+         .name
+}