Add day6, slowly

1 files changed, 36 insertions, 0 deletions

diff --git a/day6/src/main.rs b/day6/src/main.rs
new file mode 100644
index 0000000..46a148c
--- /dev/null
+++ b/day6/src/main.rs
@@ -0,0 +1,36 @@
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+fn main() -> std::io::Result<()> {
+    let file = File::open("input.txt")?;
+    let mut reader = BufReader::new(file);
+    let mut buffer = String::new();
+
+    reader.read_line(&mut buffer)?;
+
+    let mut lanternfishes: Vec<_> = buffer
+        .trim()
+        .split(',')
+        .map(|x| x.parse::<i16>().unwrap())
+        .collect::<Vec<i16>>();
+
+    for _ in 0..80 {
+        let mut n = 0;
+        for lanternfish in lanternfishes.iter_mut() {
+            if *lanternfish == 0 {
+                *lanternfish = 6;
+                n += 1;
+            } else {
+                *lanternfish -= 1;
+            }
+        }
+
+        for _ in 0..n {
+            lanternfishes.push(8);
+        }
+    }
+
+    println!("{}", lanternfishes.len());
+
+    Ok(())
+}