2 files changed, 81 insertions, 0 deletions
diff --git a/2015/rs/code/nine/src/input.txt b/2015/rs/code/nine/src/input.txt
new file mode 100644
index 0000000..97a6b63
--- /dev/null
+++ b/2015/rs/code/nine/src/input.txt
@@ -0,0 +1,28 @@
+Faerun to Tristram = 65
+Faerun to Tambi = 129
+Faerun to Norrath = 144
+Faerun to Snowdin = 71
+Faerun to Straylight = 137
+Faerun to AlphaCentauri = 3
+Faerun to Arbre = 149
+Tristram to Tambi = 63
+Tristram to Norrath = 4
+Tristram to Snowdin = 105
+Tristram to Straylight = 125
+Tristram to AlphaCentauri = 55
+Tristram to Arbre = 14
+Tambi to Norrath = 68
+Tambi to Snowdin = 52
+Tambi to Straylight = 65
+Tambi to AlphaCentauri = 22
+Tambi to Arbre = 143
+Norrath to Snowdin = 8
+Norrath to Straylight = 23
+Norrath to AlphaCentauri = 136
+Norrath to Arbre = 115
+Snowdin to Straylight = 101
+Snowdin to AlphaCentauri = 84
+Snowdin to Arbre = 96
+Straylight to AlphaCentauri = 107
+Straylight to Arbre = 14
+AlphaCentauri to Arbre = 46
diff --git a/2015/rs/code/nine/src/main.rs b/2015/rs/code/nine/src/main.rs
new file mode 100644
index 0000000..46116e0
--- /dev/null
+++ b/2015/rs/code/nine/src/main.rs
@@ -0,0 +1,53 @@
+#![feature(iter_next_chunk)]
+
+use std::collections::{HashSet, HashMap};
+use std::io::Write;
+
+static INPUT: &'static str = include_str!("input.txt");
+
+fn main() {
+  let valueified = INPUT.split('\n').filter(|s| !s.is_empty())
+    .flat_map(|s| {
+      let [rhs, dist] = s.split(" = ").next_chunk::<2>().unwrap();
+      let [from, to] = rhs.split(" to ").next_chunk::<2>().unwrap();
+      let dist = dist.parse::<usize>().unwrap();
+      [(from, to, dist), (to, from, dist)]
+    });
+
+  let paths: HashMap<&'static str, Vec<(&'static str, usize)>> = valueified
+    .map(|(a,b,c)| (a, (b, c)))
+    .fold(HashMap::new(), |mut map, (k, v)| {map.entry(k).or_default().push(v); map});
+  let mut path = Vec::new();
+  let mut bestpath = Vec::new();
+  let mut bestdist = usize::MAX;
+  let mut worstpath = Vec::new();
+  let mut worstdist = 0;
+  for start in paths.keys() {
+    path.clear();
+    path.push(*start);
+    walk_steps(&mut path, 0, &mut bestpath, &mut bestdist, &mut worstpath, &mut worstdist, &paths);
+  }
+  println!("Best route: {} with dist = {bestdist}", bestpath.join(" => "));
+  println!("Worst route: {} with dist = {worstdist}", worstpath.join(" => "));
+}
+
+fn walk_steps(path: &mut Vec<&'static str>, dist: usize, bestpath: &mut Vec<&'static str>, bestdist: &mut usize, worstpath: &mut Vec<&'static str>, worstdist: &mut usize, steps: &HashMap<&'static str, Vec<(&'static str, usize)>>) {
+  if path.len() != steps.len() {
+    let prev = path.last().unwrap();
+    for (step, stepdist) in &steps[prev] {
+      if path.contains(step) { continue; }
+      path.push(step);
+      walk_steps(path, dist + stepdist, bestpath, bestdist, worstpath, worstdist, steps);
+      path.pop();
+    }
+  } else {
+    if dist < *bestdist {
+      *bestpath = path.clone();
+      *bestdist = dist;
+    }
+    else if dist > *worstdist {
+      *worstpath = path.clone();
+      *worstdist = dist;
+    }
+  }
+}