4 files changed, 44 insertions, 0 deletions

diff --git a/2021/day6/Cargo.toml b/2021/day6/Cargo.toml
new file mode 100644
index 0000000..9957f8b
--- /dev/null
+++ b/2021/day6/Cargo.toml
@@ -0,0 +1,9 @@
+[package]
+name = "day6"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+itertools = "0.10.3"
diff --git a/2021/day6/input b/2021/day6/input
new file mode 100644
index 0000000..9bb513a
--- /dev/null
+++ b/2021/day6/input
@@ -0,0 +1 @@
+1,1,3,5,3,1,1,4,1,1,5,2,4,3,1,1,3,1,1,5,5,1,3,2,5,4,1,1,5,1,4,2,1,4,2,1,4,4,1,5,1,4,4,1,1,5,1,5,1,5,1,1,1,5,1,2,5,1,1,3,2,2,2,1,4,1,1,2,4,1,3,1,2,1,3,5,2,3,5,1,1,4,3,3,5,1,5,3,1,2,3,4,1,1,5,4,1,3,4,4,1,2,4,4,1,1,3,5,3,1,2,2,5,1,4,1,3,3,3,3,1,1,2,1,5,3,4,5,1,5,2,5,3,2,1,4,2,1,1,1,4,1,2,1,2,2,4,5,5,5,4,1,4,1,4,2,3,2,3,1,1,2,3,1,1,1,5,2,2,5,3,1,4,1,2,1,1,5,3,1,4,5,1,4,2,1,1,5,1,5,4,1,5,5,2,3,1,3,5,1,1,1,1,3,1,1,4,1,5,2,1,1,3,5,1,1,4,2,1,2,5,2,5,1,1,1,2,3,5,5,1,4,3,2,2,3,2,1,1,4,1,3,5,2,3,1,1,5,1,3,5,1,1,5,5,3,1,3,3,1,2,3,1,5,1,3,2,1,3,1,1,2,3,5,3,5,5,4,3,1,5,1,1,2,3,2,2,1,1,2,1,4,1,2,3,3,3,1,3,5
diff --git a/2021/day6/input.example b/2021/day6/input.example
new file mode 100644
index 0000000..55129f1
--- /dev/null
+++ b/2021/day6/input.example
@@ -0,0 +1 @@
+3,4,3,1,2
diff --git a/2021/day6/src/main.rs b/2021/day6/src/main.rs
new file mode 100644
index 0000000..378764e
--- /dev/null
+++ b/2021/day6/src/main.rs
@@ -0,0 +1,33 @@
+use std::env;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+
+    if args.len() != 2 {
+        eprintln!("Usage: {} <filename>", args[0]);
+        std::process::exit(1);
+    }
+    let mut smart_lanternfish: [u64; 9] = [0; 9];
+
+    let foo: String = std::fs::read_to_string(&args[1]).unwrap().parse().unwrap();
+    let mut lanternfish: Vec<u8> = Vec::new();
+    lanternfish.extend(foo.trim().split(",").map(|x| x.parse::<u8>().unwrap()));
+
+    for initial_fish in &lanternfish {
+        smart_lanternfish[*initial_fish as usize] += 1;
+    }
+
+    // println!("{:?}", smart_lanternfish);
+    for _day in 0..256 {
+        smart_lanternfish.rotate_left(1);
+        smart_lanternfish[6] += smart_lanternfish[8];
+        // println!(
+        //     "After {day:>width$} days: {lanternfish:?}",
+        //     day = _day,
+        //     width = 2,
+        //     lanternfish = smart_lanternfish
+        // );
+    }
+
+    println!("{}", smart_lanternfish.iter().sum::<u64>());
+}