Day 6

1 files changed, 45 insertions, 0 deletions

diff --git a/2017/src/bin/day06.rs b/2017/src/bin/day06.rs
new file mode 100644
index 0000000..dbc8d07
--- /dev/null
+++ b/2017/src/bin/day06.rs
@@ -0,0 +1,45 @@
+use std::collections::HashSet;
+use std::io::{self, Read};
+
+fn solve1(input: &str) -> u32 {
+    let mut banks: Vec<u32> = input.split_whitespace()
+        .map(str::parse)
+        .map(Result::unwrap)
+        .collect();
+    let mut states = HashSet::new();
+
+    for cycle in 0.. {
+        if !states.insert(banks.clone()) {
+            return cycle;
+        }
+
+        let (index, mut blocks) = banks.iter()
+            .cloned()
+            .enumerate()
+            .rev()
+            .max_by_key(|&(_, n)| n)
+            .unwrap();
+
+        banks[index] = 0;
+        for bank in (0..banks.len()).cycle().skip(index + 1) {
+            banks[bank] += 1;
+            blocks -= 1;
+            if blocks == 0 {
+                break;
+            }
+        }
+    }
+    unreachable!()
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input).unwrap();
+
+    println!("Part 1: {}", solve1(input.trim()));
+}
+
+#[test]
+fn part1() {
+    assert_eq!(5, solve1("0 2 7 0"));
+}