day22 with hashmaps

slower, but more flexible

src/tasks/day22.rs

@@ -2,11 +2,18 @@ use crate::tasks::day22::Equipment::*;
 use core::cmp::Ordering;
 use std::collections::BinaryHeap;
 use std::collections::HashMap;
+use std::time::Instant;
 
 pub fn both() {
-    let cave = Cave::create(3879, Node(8, 713, Torch));
+    let start = Instant::now();
+    let mut cave = Cave::create(3879, Node(8, 713, Torch));
+    println!("{:?}", Instant::now() - start);
+    let start = Instant::now();
     println!("Sum of erosion indexes: {}", cave.erosion_sum());
+    println!("{:?}", Instant::now() - start);
+    let start = Instant::now();
     println!("Shortest path length: {}", cave.shortest_path_length());
+    println!("{:?}", Instant::now() - start);
 }
 
 #[derive(PartialEq, Clone, Copy, Debug, Eq, Hash)]
@@ -20,8 +27,9 @@ enum Equipment {
 struct Node(usize, usize, Equipment);
 
 struct Cave {
-    map: Vec<Vec<usize>>,
+    map: HashMap<(usize, usize), usize>,
     target: Node,
+    depth: usize,
 }
 
 impl Cave {
@@ -29,31 +37,12 @@ impl Cave {
         if target.2 != Torch {
             panic!("A valid target point needs the torch equipped");
         }
-        let width = 5000;
-        let height = 5000;
-        let mut map: Vec<Vec<usize>> = Vec::with_capacity(width);
-        let mut inner_vec = Vec::with_capacity(height);
-        inner_vec.resize(height, 0);
-        map.resize(width, inner_vec);
+        let map = HashMap::with_capacity(target.0 * target.1);
 
-        for x in 0..width {
-            for y in 0..height {
-                let geo_index = match (x, y) {
-                    (0, 0) => 0,
-                    _ if target.0 == x && target.1 == y => 0,
-                    (x, 0) => x * 16807,
-                    (0, y) => y * 48271,
-                    (x, y) => map[x - 1][y] * map[x][y - 1],
-                };
-                let erosion_index = (geo_index + depth) % 20183;
-                map[x][y] = erosion_index;
-            }
-        }
-
-        Cave { map, target }
+        Cave { map, target, depth }
     }
 
-    fn erosion_sum(&self) -> usize {
+    fn erosion_sum(&mut self) -> usize {
         (0..=self.target.0)
             .map(|x| {
                 (0..=self.target.1)
@@ -63,11 +52,28 @@ impl Cave {
             .sum()
     }
 
-    fn field_type(&self, x: usize, y: usize) -> usize {
-        self.map[x][y] % 3
+    fn field_type(&mut self, x: usize, y: usize) -> usize {
+        self.erosion_index(x, y) % 3
     }
 
-    fn shortest_path_length(&self) -> usize {
+    fn erosion_index(&mut self, x: usize, y: usize) -> usize {
+        if let Some(value) = self.map.get(&(x, y)) {
+            return *value;
+        } else {
+            let geo_index = match (x, y) {
+                (0, 0) => 0,
+                _ if self.target.0 == x && self.target.1 == y => 0,
+                (x, 0) => x * 16807,
+                (0, y) => y * 48271,
+                (x, y) => self.erosion_index(x - 1, y) * self.erosion_index(x, y - 1),
+            };
+            let erosion_index = (geo_index + self.depth) % 20183;
+            self.map.insert((x, y), erosion_index);
+            return erosion_index;
+        }
+    }
+
+    fn shortest_path_length(&mut self) -> usize {
         let start = Node(0, 0, Torch);
         let mut open: BinaryHeap<State> = BinaryHeap::new();
         let mut distances: HashMap<Node, usize> = HashMap::new();
@@ -111,7 +117,7 @@ impl Cave {
         unreachable!("There is always a path");
     }
 
-    fn neighbors(&self, position: Node) -> Vec<Edge> {
+    fn neighbors(&mut self, position: Node) -> Vec<Edge> {
         let mut result = Vec::new();
         // add all variants of the current position
         result.push(Edge {
@@ -146,7 +152,7 @@ impl Cave {
         result
     }
 
-    fn equipment_allowed_for_region(&self, x: usize, y: usize, equipment: Equipment) -> bool {
+    fn equipment_allowed_for_region(&mut self, x: usize, y: usize, equipment: Equipment) -> bool {
         let field_type = self.field_type(x, y);
         match field_type {
             // rocky
@@ -159,7 +165,7 @@ impl Cave {
         }
     }
 
-    fn other_node_for_region(&self, position: Node) -> Node {
+    fn other_node_for_region(&mut self, position: Node) -> Node {
         let field_type = self.field_type(position.0, position.1);
         Node(
             position.0,