1 files changed, 68 insertions, 0 deletions
diff --git a/2016/aoc16/src/main.rs b/2016/aoc16/src/main.rs
new file mode 100644
index 0000000..c5ecd10
--- /dev/null
+++ b/2016/aoc16/src/main.rs
@@ -0,0 +1,68 @@
+fn main() {
+    let data = initial();
+    let expanded = expand_to_size(data, 35651584);
+    let check = checksum(expanded);
+    print(&check);
+}
+
+fn initial() -> Vec<bool> {
+    to_bit_vec("10001001100000001")
+}
+
+fn to_bit_vec(input: &str) -> Vec<bool> {
+    input.chars().map(|c| c == '1').collect()
+}
+
+fn expand(a: Vec<bool>) -> Vec<bool> {
+    let mut b = a.clone();
+    b.reverse();
+    b = b.iter().map(|x| !x).collect();
+
+    let mut out = a.clone();
+    out.push(false);
+    out.append(&mut b);
+    out
+}
+
+fn expand_to_size(init: Vec<bool>, size: usize) -> Vec<bool> {
+    let mut out = init.clone();
+    while out.len() < size {
+        out = expand(out);
+    }
+    out.truncate(size);
+    out
+}
+
+fn checksum(data: Vec<bool>) -> Vec<bool> {
+    let mut check: Vec<bool> = data.chunks(2).map(|x| x[0] == x[1]).collect();
+    if check.len() % 2 == 0 {
+        check = checksum(check);
+    }
+    check
+}
+
+fn print(data: &Vec<bool>) {
+    for &bit in data {
+        print!("{}", if bit {'1'} else {'0'});
+    }
+    println!("");
+}
+
+#[test]
+fn test_expand() {
+    assert_eq!(expand(to_bit_vec("1")), to_bit_vec("100"));
+    assert_eq!(expand(to_bit_vec("0")), to_bit_vec("001"));
+    assert_eq!(expand(to_bit_vec("11111")), to_bit_vec("11111000000"));
+    assert_eq!(expand(to_bit_vec("111100001010")), to_bit_vec("1111000010100101011110000"));
+}
+
+#[test]
+fn test_expand_to_size() {
+    assert_eq!(expand_to_size(to_bit_vec("10000"), 20), to_bit_vec("10000011110010000111"));
+}
+
+#[test]
+fn test_checksum() {
+    assert_eq!(checksum(to_bit_vec("10000011110010000111")), to_bit_vec("01100"));
+}
+