2 files changed, 100 insertions, 0 deletions
diff --git a/05/Cargo.toml b/05/Cargo.toml
new file mode 100644
index 0000000..4e5fdbd
--- /dev/null
+++ b/05/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "advent_05"
+version = "0.1.0"
+authors = ["Irene Knapp <ireneista@gmail.com>"]
+edition = "2018"
+
+[dependencies]
+advent_lib = { path = "../lib" }
diff --git a/05/src/main.rs b/05/src/main.rs
new file mode 100644
index 0000000..3773be8
--- /dev/null
+++ b/05/src/main.rs
@@ -0,0 +1,92 @@
+use advent_lib::prelude::*;
+
+use std::collections::BTreeSet;
+
+
+fn main() -> Result<()> {
+  let mut args = std::env::args();
+  if args.len() != 2 {
+    eprintln!("Usage: advent input");
+  }
+  let _ = args.next();
+  let filename = args.next().unwrap();
+
+  let input = advent_lib::read_lines_file(&filename)?;
+
+  let mut max_id = 0;
+  let mut found_ids = BTreeSet::new();
+
+  for line in &input {
+    let (row, column) = decode_seat(&line);
+    let id = seat_id(row, column);
+
+    found_ids.insert(id);
+
+    if id > max_id {
+      max_id = id;
+    }
+
+  }
+
+  println!("{}", max_id);
+
+  let mut is_started = false;
+
+  for i in 0 .. max_id {
+    if !is_started {
+      if found_ids.contains(&i) {
+        is_started = true;
+      }
+    } else {
+      if !found_ids.contains(&i) {
+        println!("{}", i);
+        break;
+      }
+    }
+  }
+
+  Ok(())
+}
+
+fn decode_seat(seat_spec: &str) -> (i64, i64) {
+  let mut row: i64 = 0;
+  let mut column: i64 = 0;
+
+  if seat_spec.chars().nth(0) == Some('B') {
+    row += 64;
+  }
+  if seat_spec.chars().nth(1) == Some('B') {
+    row += 32;
+  }
+  if seat_spec.chars().nth(2) == Some('B') {
+    row += 16;
+  }
+  if seat_spec.chars().nth(3) == Some('B') {
+    row += 8;
+  }
+  if seat_spec.chars().nth(4) == Some('B') {
+    row += 4;
+  }
+  if seat_spec.chars().nth(5) == Some('B') {
+    row += 2;
+  }
+  if seat_spec.chars().nth(6) == Some('B') {
+    row += 1;
+  }
+  if seat_spec.chars().nth(7) == Some('R') {
+    column += 4;
+  }
+  if seat_spec.chars().nth(8) == Some('R') {
+    column += 2;
+  }
+  if seat_spec.chars().nth(9) == Some('R') {
+    column += 1;
+  }
+
+  (row, column)
+}
+
+
+fn seat_id(row: i64, column: i64) -> i64 {
+  row * 8 + column
+}