AOC19 part 1

runs fairly fast, but does not translate easily to part 2

3 files changed, 28 insertions, 0 deletions

diff --git a/aoc19/Cargo.lock b/aoc19/Cargo.lock
new file mode 100644
index 0000000..7dc8a26
--- /dev/null
+++ b/aoc19/Cargo.lock
@@ -0,0 +1,4 @@
+[root]
+name = "aoc19"
+version = "0.1.0"
+
diff --git a/aoc19/Cargo.toml b/aoc19/Cargo.toml
new file mode 100644
index 0000000..17889e3
--- /dev/null
+++ b/aoc19/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "aoc19"
+version = "0.1.0"
+authors = ["Justin Worthe <justin.worthe@gmail.com>"]
+
+[dependencies]
diff --git a/aoc19/src/main.rs b/aoc19/src/main.rs
new file mode 100644
index 0000000..f76fce9
--- /dev/null
+++ b/aoc19/src/main.rs
@@ -0,0 +1,18 @@
+fn main() {
+    let mut elves = (0..3017957).map(|i| i+1).collect::<Vec<_>>();
+
+    let mut eliminate_mod = 1;
+    
+    while elves.len() > 1 {
+        let next_mod = if elves.len() % 2 == eliminate_mod { 0 } else { 1 };
+        elves = elves.iter()
+            .enumerate()
+            .filter(|&(i, _)| i % 2 != eliminate_mod)
+            .map(|(_, &e)| e)
+            .collect();
+        eliminate_mod = next_mod;
+    }
+
+    let elf = elves[0];
+    println!("Elf {} gets all the presents", elf);
+}