day15 solution 1

1 files changed, 38 insertions, 0 deletions

diff --git a/src/bin/day15.rs b/src/bin/day15.rs
new file mode 100644
index 0000000..648534a
--- /dev/null
+++ b/src/bin/day15.rs
@@ -0,0 +1,38 @@
+static DAY: u8 = 15;
+
+fn main() {
+    let input = advent::read_file(DAY);
+    println!("{DAY}a: {}", hash_sum(&input));
+    println!("{DAY}b: {}", 0);
+}
+
+fn hash(input: &str) -> u32 {
+    let mut value = 0;
+
+    for c in input.chars() {
+        value += c as u32;
+        value *= 17;
+        value %= 256;
+    }
+
+    value
+}
+
+fn hash_sum(input: &str) -> u32 {
+    let input = input.trim_end();
+    input.split(',')
+         .map(|x| hash(x))
+         .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test() {
+        let input = "rn=1,cm-,qp=3,cm=2,qp-,pc=4,ot=9,ab=5,pc-,pc=6,ot=7";
+        assert_eq!(hash("HASH"), 52);
+        assert_eq!(hash_sum(input), 1320);
+    }
+}