solution: day5

src/bin/05.rs

@@ -0,0 +1,78 @@
+use hashbrown::HashMap;
+use itertools::Itertools;
+use md5::{Digest, Md5};
+
+pub fn part_one(input: &str) -> Option<String> {
+    let key = input.trim().as_bytes();
+    let mut hasher = Md5::new();
+    let mut count = 0;
+    let mut res = String::new();
+
+    for x in 0..std::u64::MAX {
+        hasher.update(key);
+        hasher.update(x.to_string().as_bytes());
+        let output = hasher.finalize_reset();
+
+        if output.starts_with(&[0, 0]) && output[2] <= 0x0F {
+            count += 1;
+            res.push_str(&format!("{:02x}", output[2])[1..]);
+        }
+
+        if count == 8 {
+            break;
+        }
+    }
+
+    Some(res)
+}
+pub fn part_two(input: &str) -> Option<String> {
+    let key = input.trim().as_bytes();
+    let mut hasher = Md5::new();
+    let mut res = HashMap::new();
+
+    for x in 0..std::u64::MAX {
+        hasher.update(key);
+        hasher.update(x.to_string().as_bytes());
+        let output = hasher.finalize_reset();
+
+        if output.starts_with(&[0, 0]) && output[2] <= 0x0F {
+            let (p, c) = format!("{:02x}{:02x}", output[2], output[3])[1..3]
+                .chars()
+                .next_tuple()
+                .unwrap();
+            if ('0'..='7').contains(&p) && !res.contains_key(&p) {
+                res.insert(p, c);
+            }
+        }
+
+        if res.len() == 8 {
+            break;
+        }
+    }
+
+    Some(
+        res.iter()
+            .sorted_by(|a, b| a.0.cmp(b.0))
+            .map(|(_, v)| v)
+            .collect(),
+    )
+}
+fn main() {
+    let input = &aoc::read_file("inputs", 5);
+    aoc::solve!(1, part_one, input);
+    aoc::solve!(2, part_two, input);
+}
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        let input = aoc::read_file("examples", 5);
+        assert_eq!(part_one(&input), Some("18f47a30".to_string()));
+    }
+    #[test]
+    fn test_part_two() {
+        let input = aoc::read_file("examples", 5);
+        assert_eq!(part_two(&input), Some("05ace8e3".to_string()));
+    }
+}