Add solutions to day 19.

2016/day-19/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day-19"
+version = "0.1.0"
+authors = ["Bert Peters <bert.ljpeters@gmail.com>"]
+
+[dependencies]

2016/day-19/src/main.rs

@@ -0,0 +1,41 @@
+// Part 1 is the josephus function
+fn josephus(input: u32)
+{
+    let input_2 = 1 << (31 - input.leading_zeros());
+
+    let remainder = input - input_2;
+
+    println!("Position for {} is {}", input, remainder * 2 + 1);
+}
+
+fn power_3(input: u32) -> u32
+{
+    let mut base = 1;
+    while 3 * base < input {
+        base = base * 3;
+    }
+
+    return base;
+}
+
+// Part two is similar, but in base 3.
+fn alternative(input: u32)
+{
+    let log = power_3(input);
+    let remainder = input - log;
+
+    let pos;
+
+    if remainder <= log {
+        pos = remainder;
+    } else {
+        pos = 2 * remainder - log;
+    }
+
+    println!("Alternative for {} is: {}", input, pos);
+}
+
+fn main() {
+    josephus(3014603);
+    alternative(3014603);
+}