From 2599a5686198ed6af783c7a9a1a67ab71750f156 Mon Sep 17 00:00:00 2001
From: dece <shgck@pistache.land>
Date: Mon, 6 Dec 2021 14:11:01 +0100
Subject: [PATCH] Day 6 in Rust

---
 2021/rust/.gitignore      |  1 +
 2021/rust/Cargo.lock      |  7 +++++++
 2021/rust/Cargo.toml      |  8 ++++++++
 2021/rust/src/bin/day6.rs | 30 ++++++++++++++++++++++++++++++
 4 files changed, 46 insertions(+)
 create mode 100644 2021/rust/.gitignore
 create mode 100644 2021/rust/Cargo.lock
 create mode 100644 2021/rust/Cargo.toml
 create mode 100644 2021/rust/src/bin/day6.rs

diff --git a/2021/rust/.gitignore b/2021/rust/.gitignore
new file mode 100644
index 0000000..2f7896d
--- /dev/null
+++ b/2021/rust/.gitignore
@@ -0,0 +1 @@
+target/
diff --git a/2021/rust/Cargo.lock b/2021/rust/Cargo.lock
new file mode 100644
index 0000000..b21cc6a
--- /dev/null
+++ b/2021/rust/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "rust"
+version = "0.1.0"
diff --git a/2021/rust/Cargo.toml b/2021/rust/Cargo.toml
new file mode 100644
index 0000000..1ec6963
--- /dev/null
+++ b/2021/rust/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/2021/rust/src/bin/day6.rs b/2021/rust/src/bin/day6.rs
new file mode 100644
index 0000000..bb48799
--- /dev/null
+++ b/2021/rust/src/bin/day6.rs
@@ -0,0 +1,30 @@
+use std::io;
+
+fn main() {
+    let mut text = String::new();
+    io::stdin().read_line(&mut text).unwrap();
+    let mut data = vec![0u64; 9];
+    for c in text.strip_suffix("\n").unwrap().split(",") {
+        data[str::parse::<usize>(c).unwrap()] += 1;
+    }
+    for _ in 0..80 {
+        step(&mut data);
+    }
+    println!("{}", data.iter().sum::<u64>());
+    for _ in 80..256 {
+        step(&mut data);
+    }
+    println!("{}", data.iter().sum::<u64>());
+}
+
+fn step(data: &mut Vec<u64>) {
+    let d0 = data[0];
+    let mut prev = data[8];
+    for d in (0..=7).rev() {
+        let temp = data[d];
+        data[d] = prev;
+        prev = temp;
+    }
+    data[6] += d0;
+    data[8] = d0;
+}