1 files changed, 36 insertions, 0 deletions
diff --git a/aoc15/src/main.rs b/aoc15/src/main.rs
new file mode 100644
index 0000000..3db59ea
--- /dev/null
+++ b/aoc15/src/main.rs
@@ -0,0 +1,36 @@
+extern crate regex;
+
+use regex::Regex;
+use std::io::BufReader;
+use std::io::prelude::*;
+use std::fs::File;
+
+
+fn main() {
+    let gears = read_file();
+    let pass = (0..).find(|&i| can_pass(&gears, i)).unwrap();
+    println!("First pass at t={}", pass);
+}
+
+fn can_pass(gears: &Vec<(i32, i32)>, time: i32) -> bool {
+    for i in 0..gears.len() {
+        let (gear_pos, gear_size) = gears[i];
+        if (gear_pos + time + i as i32 + 1) % gear_size != 0 {
+            return false;
+        }
+    }
+    true
+}
+
+fn read_file() -> Vec<(i32, i32)> {
+    let file = BufReader::new(File::open("input.txt").unwrap());
+    let line_regex = Regex::new(r"Disc #\d+ has (\d+) positions; at time=0, it is at position (\d+).").unwrap();
+    file.lines()
+        .map(|line| line.unwrap().trim().to_string())
+        .filter(|line| line.len() > 0)
+        .map(|line| {
+            let cap = line_regex.captures(line.as_ref()).unwrap();
+            (cap.at(2).unwrap().parse().unwrap(), cap.at(1).unwrap().parse().unwrap())
+        })
+        .collect()
+}