Update day 19.

2016/19/src/main.rs

@@ -1,14 +1,10 @@
 use std::collections::VecDeque;
 
 
-fn main() {
-    let input = 3018458;
-
-
-    // Part 1.
+pub fn steal_left(elf_count: usize) -> usize {
     let mut elfs = Vec::new();
 
-    for i in 1..input + 1 {
+    for i in 1..elf_count + 1 {
         elfs.push(i);
     }
 
@@ -26,25 +22,80 @@ fn main() {
         }
     }
 
-    println!("winner={:?}", elfs[0]);
+    elfs[0]
+}
 
-
-    // Part 2.
+pub fn steal_across(elf_count: usize) -> usize {
     let mut elfs = VecDeque::new();
 
-    for i in 1..input + 1 {
+    for i in 1..elf_count + 1 {
         elfs.push_back(i);
     }
 
     while elfs.len() > 1 {
         let buddy = elfs.len() / 2;
 
-        elfs.remove(buddy);
+        let b = elfs.remove(buddy);
 
         let elf = elfs.pop_front().unwrap();
 
+        println!("{} ! {}", elf, b.unwrap());
+
         elfs.push_back(elf);
     }
 
-    println!("winner={:?}", elfs[0]);
+    elfs[0]
+}
+
+pub fn steal_across_v2(elf_count: usize) -> usize {
+    let mut elfs = Vec::new();
+
+    for i in 1..elf_count + 1 {
+        elfs.push(i);
+    }
+
+    elfs[0]
+}
+
+fn main() {
+    let input = 3018458;
+
+    // Part 1.
+    println!("winner={:?}", steal_left(input));
+
+    // Part 2.
+    println!("winner={:?}", steal_across(25));
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_steal_left() {
+        assert_eq!(3, steal_left(5));
+
+        assert_eq!(489, steal_left(500));
+        assert_eq!(977, steal_left(1_000));
+        assert_eq!(953, steal_left(1_500));
+    }
+
+    #[test]
+    fn test_steal_across() {
+        assert_eq!(2, steal_across(5));
+
+        assert_eq!(271, steal_across(500));
+        assert_eq!(271, steal_across(1_000));
+        assert_eq!(813, steal_across(1_500));
+    }
+
+    #[test]
+    fn test_steal_across_v2() {
+        assert_eq!(2, steal_across_v2(5));
+
+        assert_eq!(271, steal_across_v2(500));
+        assert_eq!(271, steal_across_v2(1_000));
+        assert_eq!(813, steal_across_v2(1_500));
+    }
 }