Optimized with a maintained HouseLayout

src/main.rs

@@ -66,58 +66,112 @@ impl House {
     }
 }
 
+struct HouseLayout<'a> {
+    city: &'a City,
+    reachable: Vec<u16>,
+    houses: Vec<House>,
+    reachable_houses: usize
+}
+
+impl<'a> HouseLayout<'a> {
+    pub fn new(city: &'a City) -> Self {
+        HouseLayout { city, reachable: vec![0; SIZE * SIZE], houses: Vec::new(), reachable_houses: 0 }
+    }
+
+    pub fn cover_count(&self, house: House) -> u16 {
+        self.reachable[house.y * SIZE + house.x]
+    }
+
+    pub fn is_covered(&self, house: House) -> bool {
+        self.cover_count(house) > 0
+    }
+
+    pub fn add_house(&mut self, house: House) -> usize {
+        for y in (house.y as i32 - 500).max(0)..=(house.y as i32 + 500).min((SIZE - 1) as i32) {
+            for x in (house.x as i32 - 500).max(0)..=(house.x as i32 + 500).min((SIZE - 1) as i32) {
+                let index = y as usize * SIZE + x as usize;
+
+                if self.reachable[index] == 0 && self.city.is_house_xy(x as usize, y as usize) {
+                    self.reachable_houses += 1;
+                }
+
+                self.reachable[index] += 1;
+            }
+        }
+        self.houses.push(house);
+        self.houses.len() - 1
+    }
+
+    pub fn remove_house(&mut self, index: usize) {
+        let house = self.houses.swap_remove(index);
+
+        for y in (house.y as i32 - 500).max(0)..=(house.y as i32 + 500).min((SIZE - 1) as i32) {
+            for x in (house.x as i32 - 500).max(0)..=(house.x as i32 + 500).min((SIZE - 1) as i32) {
+                let index = y as usize * SIZE + x as usize;
+
+                self.reachable[index] -= 1;
+
+                if self.reachable[index] == 0 && self.city.is_house_xy(x as usize, y as usize) {
+                    self.reachable_houses -= 1;
+                }
+            }
+        }
+    }
+
+    pub fn is_valid(&self) -> bool {
+        self.reachable_houses == self.city.buyable_house_count
+    }
+
+    pub fn price(&self) -> u32 {
+        get_price(self.city, &self.houses)
+    }
+
+    pub fn houses(&self) -> &Vec<House> {
+        &self.houses
+    }
+}
+
 fn main() {
     let city = City::read_from_file("01.in");
 
+    const AROUND_RANGE: i32 = 200;
+    const MAX_CANDIDATES: usize = 200;
+    //const MAX_FAILED_ITERATIONS: usize = 50;
+    println!("Params: AROUND_RANGE {}, MAX_CANDIDATES {}", AROUND_RANGE, MAX_CANDIDATES);
+    eprintln!("Params: AROUND_RANGE {}, MAX_CANDIDATES {}", AROUND_RANGE, MAX_CANDIDATES);
+
     let mut best_price: Option<u32> = None;
     loop {
         let seed: u64 = thread_rng().gen();
         eprintln!("Starting seed {}", seed);
 
         let mut rng = StdRng::seed_from_u64(seed);
-        let mut reachable = vec![false; SIZE * SIZE];
+        let mut layout = HouseLayout::new(&city);
-        let mut houses: Vec<House> = Vec::new();
-        let mut claimed_houses = 0;
         loop {
             loop {
                 let x = rng.gen_range(0..SIZE);
                 let y = rng.gen_range(0..SIZE);
                 let house = House::new(x, y);
-                if city.is_house_xy(x, y) && !reachable[y * SIZE + x] {
+                if city.is_house_xy(x, y) && !layout.is_covered(house) {
-                    for y in (house.y as i32 - 500).max(0)..=(house.y as i32 + 500).min((SIZE - 1) as i32) {
+                    layout.add_house(house);
-                        for x in (house.x as i32 - 500).max(0)..=(house.x as i32 + 500).min((SIZE - 1) as i32) {
-                            let index = y as usize * SIZE + x as usize;
-                            if !reachable[index] {
-                                reachable[index] = true;
-                                if city.is_house_xy(x as usize, y as usize) {
-                                    claimed_houses += 1;
-                                }
-                            }
-                        }
-                    }
-                    houses.push(house);
-                    //eprintln!("{} houses", houses.len());
                     break;
                 }
             }
 
-            let finished = claimed_houses == city.get_house_count();
+            if layout.is_valid() {
-
-            if finished {
                 break;
             }
         }
 
-        let mut price = get_price(&city, &houses);
+        eprintln!("Finished random init, price: {}", layout.price());
-        eprintln!("Finished random init, price: {}", price);
+
+        let mut untried_houses = layout.houses().clone();
+        untried_houses.shuffle(&mut rng);
 
-        const AROUND_RANGE: i32 = 50;
+        while untried_houses.len() > 0 {
-        const MAX_CANDIDATES: usize = 20;
+            let house = untried_houses.pop().unwrap();
-        const MAX_FAILED_ITERATIONS: usize = 50;
+            let mut house_index = layout.houses().iter().position(|x| *x == house).unwrap();
 
-        let mut failed_iterations = 0;
-        while failed_iterations < MAX_FAILED_ITERATIONS {
-            let house = &houses.choose(&mut rng).unwrap();
             let mut new_candidates = Vec::new();
             for delta_y in -AROUND_RANGE..=AROUND_RANGE {
                 for delta_x in -AROUND_RANGE..=AROUND_RANGE {
@@ -131,45 +185,61 @@ fn main() {
 
             new_candidates.sort_by(|a, b| city.get_price(&a).cmp(&city.get_price(&b)));
             if new_candidates.len() == 0 {
-                eprintln!("Did not find candidate");
+                //eprintln!("Did not find candidate");
             } else {
                 for (i, &candidate) in new_candidates.iter().enumerate() {
                     if i > MAX_CANDIDATES {
+                        //eprintln!("No valid candidate");
                         break;
                     }
 
-                    eprint!("Found candidate {}...", i);
+                    //eprint!("Found candidate {}...", i);
-                    let mut new_houses: Vec<_> = houses.to_vec().into_iter().filter(|h| &h != house).collect();
+
-                    new_houses.push(candidate);
+                    let old_price = layout.price();
-                    // TODO: This is_valid check could be way more efficient
+                    layout.remove_house(house_index);
-                    if let Some(new_price) = is_valid(&city, &new_houses) {
+
-                        let price_diff = new_price as i64 - price as i64;
+                    if layout.is_valid() {
-                        eprintln!(" candidate is valid, price diff: {}.", price_diff);
+                        // The candidate is not needed, the house was unnecessary
+                        let new_price = layout.price();
+                        let price_diff = new_price as i64 - old_price as i64;
+                        //eprintln!(" candidate is valid, price diff: {}.", price_diff);
+                        eprintln!("Removed a house, diff {}", price_diff);
                         eprintln!("Improved price: {}", new_price);
-                        price = new_price;
+                        untried_houses = layout.houses().clone();
-                        houses = new_houses;
+                        untried_houses.shuffle(&mut rng);
-                        failed_iterations = 0;
+                        break;
+                    }
+
+                    let candidate_index = layout.add_house(candidate);
+
+                    if layout.is_valid() {
+                        let new_price = layout.price();
+                        let price_diff = new_price as i64 - old_price as i64;
+                        //eprintln!(" candidate is valid, price diff: {}.", price_diff);
+                        eprintln!("Improved price: {}", new_price);
+                        untried_houses = layout.houses().clone();
+                        untried_houses.shuffle(&mut rng);
                         break;
                     } else {
-                        eprintln!(" candidate is invalid.");
+                        //eprintln!(" candidate is invalid.");
+                        layout.remove_house(candidate_index);
+                        house_index = layout.add_house(house);
                     }
                 }
             }
-
-            // Successful iterations always break
-            failed_iterations += 1;
         }
 
+        let price = layout.price();
         if best_price.is_none() || price < best_price.unwrap() {
             best_price = Some(price);
             eprintln!("Finished randomization, price: {}, new best, printing", price);
             println!("Price {}, seed {}", price, seed);
-            print_houses(&houses);
+            print_houses(&layout.houses());
             println!();
         } else {
             eprintln!("Finished randomization, price: {}, printing", price);
             println!("Price {}, seed {}", price, seed);
-            print_houses(&houses);
+            print_houses(&layout.houses());
             println!();
         }
     }