1 files changed, 42 insertions, 0 deletions
diff --git a/2016/aoc19/src/main.rs b/2016/aoc19/src/main.rs
new file mode 100644
index 0000000..1930d8d
--- /dev/null
+++ b/2016/aoc19/src/main.rs
@@ -0,0 +1,42 @@
+fn main() {
+    part1();
+    part2();
+}
+
+fn part1() {
+    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 in part 1", elf);
+}
+
+fn part2() {
+    let mut elves = (0..3017957).map(|i| i+1).collect::<Vec<_>>();
+
+    let mut i = 0;
+    while elves.len() > 1 {
+        i = i % elves.len();
+        let to_eliminate = (i + elves.len() / 2) % elves.len();
+//        println!("Elf {} is taking presents from elf {}", elves[i], elves[to_eliminate]);
+        elves.remove(to_eliminate);
+        if to_eliminate > i {
+            i += 1;
+        }
+    }
+
+    let elf = elves[0];
+    println!("Elf {} gets all the presents in part 2", elf);
+
+}