day 6 solutions

src/day06.rs

@@ -0,0 +1,41 @@
+// ==== day 6
+
+use crate::utils;
+use anyhow::Result;
+use std::collections::{HashMap, HashSet};
+
+fn count_uniq_alpha_chars(s: &str) -> usize {
+    let seen: HashSet<usize> = s
+        .chars()
+        .filter(|c| c.is_alphabetic())
+        .map(|c| c as usize)
+        .collect();
+    seen.len()
+}
+
+fn count_common_answers(s: &str) -> usize {
+    let mut seen: HashMap<char, usize> = HashMap::new();
+    for l in s.lines() {
+        for c in l.chars().filter(|c| c.is_alphabetic()) {
+            *seen.entry(c).or_insert(0) += 1;
+        }
+    }
+    let total = s.lines().count();
+    seen.values().filter(|v| *v == &total).count()
+}
+
+pub fn run() -> Result<(usize, usize)> {
+    let data = utils::read_file("data/input-06.txt")?;
+    let answers = utils::read_i64s("data/output-06.txt")?;
+
+    // parse into an array of Passport{}
+    let p1 = data.split("\n\n").map(|s| count_uniq_alpha_chars(s)).sum();
+
+    // count passports with all req'd and validated fields
+    let p2 = data.split("\n\n").map(|s| count_common_answers(s)).sum();
+
+    assert_eq!(p1, answers[0] as usize);
+    assert_eq!(p2, answers[1] as usize);
+
+    Ok((p1, p2))
+}