2016/19

2016/19/Cargo.lock

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+[root]
+name = "19"
+version = "0.1.0"
+

2016/19/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "19"
+version = "0.1.0"
+authors = ["logaritmisk <anders.e.olsson@gmail.com>"]
+
+[dependencies]

2016/19/src/main.rs

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+use std::collections::VecDeque;
+
+
+fn main() {
+    let input = 3018458;
+
+
+    // Part 1.
+    let mut elfs = Vec::new();
+
+    for i in 1..input + 1 {
+        elfs.push(i);
+    }
+
+    while elfs.len() > 1 {
+        let odd = elfs.len() % 2 != 0;
+
+        elfs = elfs.iter()
+            .enumerate()
+            .filter(|&(i, _)| i % 2 == 0)
+            .map(|(_, e)| *e)
+            .collect();
+
+        if elfs.len() > 1 && odd {
+            elfs.remove(0);
+        }
+    }
+
+    println!("winner={:?}", elfs[0]);
+
+
+    // Part 2.
+    let mut elfs = VecDeque::new();
+
+    for i in 1..input + 1 {
+        elfs.push_back(i);
+    }
+
+    while elfs.len() > 1 {
+        let buddy = elfs.len() / 2;
+
+        elfs.remove(buddy);
+
+        let elf = elfs.pop_front().unwrap();
+
+        elfs.push_back(elf);
+    }
+
+    println!("winner={:?}", elfs[0]);
+}