1 files changed, 85 insertions, 0 deletions
diff --git a/src/bin/day5.rs b/src/bin/day5.rs
new file mode 100644
index 0000000..ea9a58b
--- /dev/null
+++ b/src/bin/day5.rs
@@ -0,0 +1,85 @@
+fn main() {
+    let input = advent::read_lines(5);
+    println!("5a: {}", count_nice(&input, is_nice));
+    println!("5b: {}", count_nice(&input, is_nice2));
+}
+
+fn is_nice(word: &str) -> bool {
+    let mut prev = ' ';
+    let mut vowel_count = 0;
+    let mut double_letter = false;
+
+    for c in word.chars() {
+        if ['a', 'e', 'i', 'o', 'u'].contains(&c) {
+            vowel_count += 1;
+        }
+        if prev == c {
+            double_letter = true;
+        }
+        let pair = format!("{}{}", prev, c);
+        if ["ab".to_string(), "cd".to_string(), "pq".to_string(), "xy".to_string()].contains(&pair) {
+            return false;
+        }
+
+        prev = c;
+    }
+    double_letter && vowel_count >= 3
+}
+
+fn has_two_pairs(word: &str) -> bool {
+    let mut prev = ' ';
+
+    for c in word.chars() {
+        let pair = format!("{}{}", prev, c);
+
+        if word.matches(&pair).count() > 1 {
+            return true;
+        }
+
+        prev = c;
+    }
+    false
+}
+
+fn has_one_letter_repeat(word: &str) -> bool {
+    let mut prev = ' ';
+    let mut prevprev = ' ';
+
+    for c in word.chars() {
+        if c == prevprev {
+            return true;
+        }
+        prevprev = prev;
+        prev = c;
+    }
+    false
+}
+
+fn is_nice2(word: &str) -> bool {
+    has_two_pairs(word) && has_one_letter_repeat(word)
+}
+
+fn count_nice(input: &[String], f: fn(&str) -> bool) -> usize {
+    input.iter()
+         .filter(|&x| f(x))
+         .count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        assert!(is_nice("ugknbfddgicrmopn"));
+        assert!(is_nice("aaa"));
+        assert!(!is_nice("jchzalrnumimnmhp"));
+        assert!(!is_nice("haegwjzuvuyypxyu"));
+        assert!(!is_nice("dvszwmarrgswjxmb"));
+
+        assert!(is_nice2("qjhvhtzxzqqjkmpb"));
+        assert!(is_nice2("xxyxx"));
+        assert!(!is_nice2("uurcxstgmygtbstg"));
+        assert!(!is_nice2("ieodomkazucvgmuy"));
+    }
+}