10

1 files changed, 67 insertions, 0 deletions

diff --git a/10/src/main.rs b/10/src/main.rs
new file mode 100644
index 0000000..d504711
--- /dev/null
+++ b/10/src/main.rs
@@ -0,0 +1,67 @@
+use advent_lib::prelude::*;
+
+use std::convert::TryFrom;
+
+
+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 adaptors: Vec<i64> = Vec::new();
+  for line in &input {
+    adaptors.push(line.parse::<i64>().unwrap());
+  }
+  adaptors.sort();
+
+  let mut buckets = Vec::new();
+  buckets.push(0);
+  buckets.push(0);
+  buckets.push(0);
+  buckets.push(0);
+
+  for i in 0 .. adaptors.len() {
+    let mut prev_joltage = 0;
+    if i > 0 {
+      prev_joltage = adaptors[i - 1];
+    }
+    let difference = adaptors[i] - prev_joltage;
+    buckets[usize::try_from(difference).unwrap()] += 1;
+  }
+
+  buckets[3] += 1;
+
+  println!("{}", buckets[1]*buckets[3]);
+
+  let mut reversed_adaptors = Vec::new();
+  for i in 0 .. adaptors.len() {
+    reversed_adaptors.push(adaptors[adaptors.len() - i - 1]);
+  }
+  reversed_adaptors.push(0);
+
+  let mut memoized_counts: Vec<i64> = Vec::new();
+  memoized_counts.push(1);
+
+  for i in 1 .. reversed_adaptors.len() {
+    let mut count = 0;
+    for j in 1 .. i+1 {
+      let difference = reversed_adaptors[i - j] - reversed_adaptors[i];
+      if difference <= 3 {
+        count += memoized_counts[i - j];
+      } else {
+        break;
+      }
+    }
+    memoized_counts.push(count);
+  }
+
+  println!("{}", memoized_counts[memoized_counts.len()-1]);
+
+  Ok(())
+}
+