From 81bf01201ad9edc5ebfa54091146a09ea60d2fd4 Mon Sep 17 00:00:00 2001
From: mat ess <mat@mat.services>
Date: Mon, 12 Dec 2022 22:10:32 -0500
Subject: [PATCH] Finish day 12

---
 src/main.rs | 58 +++++++++++++++++++++++++++++++++--------------------
 1 file changed, 36 insertions(+), 22 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index a2909bb..3349f53 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::{HashMap, HashSet, VecDeque};
 use std::fmt::Debug;
 use std::fs;
 use std::ops::{Range, RangeInclusive};
@@ -279,11 +279,12 @@ solutions! {
         // day 12 part 1
         |input| {
             let map = Map::from_string(input);
-            map.navigate().into()
+            map.navigate(map.start).unwrap().into()
         },
         // day 12 part 1
         |input| {
-            todo!()
+            let map = Map::from_string(input);
+            map.best_navigate().into()
         },
     ]
 }
@@ -296,27 +297,40 @@ struct Map {
 }
 
 impl Map {
-    fn navigate(self) -> u64 {
-        // this is fuckin buggy
-        let (mut x, mut y) = self.start;
-        let mut last = (x, y);
-        let mut prior = (x, y);
-        let mut steps = 0;
-        while (x, y) != self.end {
+    fn best_navigate(self) -> u64 {
+        self.map
+            .iter()
+            .enumerate()
+            .flat_map(|(x, row)| {
+                row.iter()
+                    .enumerate()
+                    .map(move |(y, level)| (x, y, *level))
+                    .filter_map(|(x, y, level)| if level == 0 { Some((x, y)) } else { None })
+            })
+            .flat_map(|start| self.navigate(start))
+            .min()
+            .unwrap()
+    }
+
+    fn navigate(&self, start: (usize, usize)) -> Option<u64> {
+        let mut q = VecDeque::new();
+        let mut visited = HashSet::new();
+        visited.insert(start);
+        q.push_back((start, 0));
+        while !q.is_empty() {
+            let ((x, y), steps) = q.pop_front().unwrap();
             let level = self.map[x][y];
-            print!("moving from ({x},{y}) to ");
-            prior = last;
-            last = (x, y);
-            (x, y, _) = self
-                .neighbors(x, y)
-                .filter(|(_, _, neighbor)| (level..=level + 1).contains(neighbor))
-                .filter(|(nx, ny, _)| (*nx, *ny) != prior)
-                .max_by_key(|(_, _, neighbor)| *neighbor)
-                .unwrap();
-            println!("({x},{y})");
-            steps += 1;
+            if (x, y) == self.end {
+                return Some(steps);
+            }
+            for (nx, ny, nlevel) in self.neighbors(x, y) {
+                if !visited.contains(&(nx, ny)) && nlevel <= level + 1 {
+                    visited.insert((nx, ny));
+                    q.push_back(((nx, ny), steps + 1))
+                }
+            }
         }
-        steps
+        None
     }
 
     fn neighbors(&self, x: usize, y: usize) -> impl Iterator<Item = (usize, usize, isize)> {