Řešení KSP úlohy 33-3-4 Obsazování území
https://ksp.mff.cuni.cz/h/ulohy/33/zadani3.html#task-33-3-4
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321 lines
13 KiB
321 lines
13 KiB
use std::collections::HashSet;
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use rand::prelude::{SliceRandom, StdRng};
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use crate::city::{Rectangle, HOUSE_RANGE, House, HouseLayout};
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use itertools::iproduct;
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pub enum RectangleSearchError {
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Useless,
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Unsatisfiable,
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}
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pub fn iterate_improvements(mut layout: &mut HouseLayout, mut rng: &mut StdRng, print_progress: bool, merge_first: bool) -> bool {
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#[derive(Eq, PartialEq)]
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enum LastStep {
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None,
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MovingIndividual,
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MergingPairs,
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}
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let mut improved = false;
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let mut first_iteration = true;
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let mut last_improved_step = LastStep::None;
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loop {
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if merge_first && first_iteration {
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first_iteration = false;
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} else {
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if last_improved_step == LastStep::MovingIndividual { break; }
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if print_progress {
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eprintln!("Starting moving individual houses...");
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}
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if improve_move_individual_houses(&mut layout, &mut rng) {
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last_improved_step = LastStep::MovingIndividual;
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improved = true;
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}
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if print_progress {
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eprintln!("Finished moving individual houses...");
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}
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}
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if last_improved_step == LastStep::MergingPairs { break; }
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if print_progress {
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eprintln!("Starting pairwise house merge...");
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}
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if improve_merge_pairwise(&mut layout, print_progress) {
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last_improved_step = LastStep::MergingPairs;
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improved = true;
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}
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if print_progress {
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eprintln!("Finished pairwise house merge");
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}
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if last_improved_step == LastStep::None { break; }
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}
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improved
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}
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fn get_valid_move_rectangle_multiple(layout: &HouseLayout, houses: &Vec<House>) -> Result<Rectangle, RectangleSearchError> {
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// This is a generalization of get_valid_move_rectangle, it's basically the same thing,
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// just with a dynamic rectangles_containing_count
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// We first establish a bounding box for an that has to be covered if all houses are removed.
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let mut covered_rect: Option<Rectangle> = None;
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for house in houses {
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let range_rect = house.range_rectangle(layout.city);
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for y in range_rect.top..=range_rect.bottom {
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for x in range_rect.left..=range_rect.right {
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// We count how many rectangles of houses contain this xy position.
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let mut rectangles_containing_count = 0;
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for house in houses {
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let rect = house.range_rectangle(layout.city);
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if rect.is_inside(x, y) {
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rectangles_containing_count += 1;
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}
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}
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// If this house is covered by the exact amount of rectangles,
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// then removing all input houses would uncover this position.
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// It cannot be less than the rectangle count, and more means there
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// is another house covering it as well.
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if layout.cover_count_xy(x, y) == rectangles_containing_count && layout.city.is_house_xy(x, y) {
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if let Some(cover) = &mut covered_rect {
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cover.left = cover.left.min(x);
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cover.right = cover.right.max(x);
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cover.top = cover.top.min(y);
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cover.bottom = cover.bottom.max(y);
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} else {
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covered_rect = Some(Rectangle { left: x, right: x, top: y, bottom: y });
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}
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}
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}
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}
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};
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if covered_rect.is_none() {
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// Unnecessary set of houses.
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return Err(RectangleSearchError::Useless);
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}
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let covered_rect = covered_rect.unwrap();
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let height_margin = HOUSE_RANGE as i32 - covered_rect.height() as i32;
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let width_margin = HOUSE_RANGE as i32 - covered_rect.width() as i32;
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let top = (covered_rect.top as i32 - height_margin).max(0) as usize;
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let left = (covered_rect.left as i32 - width_margin).max(0) as usize;
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let bottom = (covered_rect.bottom + height_margin as usize).min(layout.city.height() - 1);
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let right = (covered_rect.right + width_margin as usize).min(layout.city.width() - 1);
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if top > bottom || left > right {
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// Unsatisfiable rectangle by one house
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return Err(RectangleSearchError::Unsatisfiable);
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}
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Ok(Rectangle { left, right, top, bottom })
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}
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pub fn get_valid_move_rectangle(layout: &HouseLayout, house: House) -> Result<Rectangle, RectangleSearchError> {
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// We first establish a bounding box for an that has to be covered if the house is removed.
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let mut covered_rect: Option<Rectangle> = None;
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let range_rect = house.range_rectangle(layout.city);
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for y in range_rect.top..=range_rect.bottom {
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for x in range_rect.left..=range_rect.right {
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if layout.cover_count_xy(x, y) == 1 && layout.city.is_house_xy(x, y) {
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// This house is only covered by the house, it has to be covered from the new position as well.
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if let Some(cover) = &mut covered_rect {
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cover.left = cover.left.min(x);
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cover.right = cover.right.max(x);
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cover.top = cover.top.min(y);
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cover.bottom = cover.bottom.max(y);
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} else {
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covered_rect = Some(Rectangle { left: x, right: x, top: y, bottom: y });
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}
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}
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}
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}
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if covered_rect.is_none() {
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return Err(RectangleSearchError::Useless);
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}
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let covered_rect = covered_rect.unwrap();
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// The distance of the rectangle from the original box tells us how much the house can move.
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let dist_left = covered_rect.left - range_rect.left;
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let dist_right = range_rect.right - covered_rect.right;
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let dist_top = covered_rect.top - range_rect.top;
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let dist_bottom = range_rect.bottom - covered_rect.bottom;
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let left = if house.x <= dist_right { 0 } else { house.x - dist_right };
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let right = if house.x >= layout.city.width() - 1 - dist_left { layout.city.width() - 1 } else { house.x + dist_left };
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let top = if house.y <= dist_bottom { 0 } else { house.y - dist_bottom };
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let bottom = if house.y >= layout.city.height() - 1 - dist_top { layout.city.height() - 1 } else { house.y + dist_top };
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let valid_move_rectangle = Rectangle {
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left,
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right,
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top,
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bottom,
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};
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Ok(valid_move_rectangle)
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}
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pub fn improve_move_individual_houses(layout: &mut HouseLayout, mut rng: &mut StdRng) -> bool {
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let mut improved = false;
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let mut untried_houses = layout.houses().clone();
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untried_houses.shuffle(&mut rng);
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while untried_houses.len() > 0 {
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let house = untried_houses.pop().unwrap();
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let house_index = layout.houses().iter().position(|x| *x == house).unwrap();
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let move_rectangle = match get_valid_move_rectangle(&layout, house) {
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Ok(move_rectangle) => move_rectangle,
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Err(RectangleSearchError::Useless) => {
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//let old_price = layout.price();
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layout.remove_house(house_index);
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//let new_price = layout.price();
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//let price_diff = new_price as i64 - old_price as i64;
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//eprintln!(" candidate is valid, price diff: {}.", price_diff);
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//eprintln!("Removed a house (useless), diff {}", price_diff);
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//eprintln!("Improved price: {}", new_price);
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improved = true;
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untried_houses = layout.houses().clone();
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untried_houses.shuffle(&mut rng);
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continue;
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}
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_ => unreachable!()
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};
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// TODO: Not needed, can just store best
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let mut new_candidates = Vec::new();
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for new_y in move_rectangle.top..=move_rectangle.bottom {
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for new_x in move_rectangle.left..=move_rectangle.right {
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if layout.city.is_house_xy(new_x, new_y) && layout.city.get_price_xy(new_x, new_y) < layout.city.get_price(house) {
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new_candidates.push(House::new(new_x, new_y));
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}
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}
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}
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new_candidates.sort_by(|a, b| layout.city.get_price(*a).cmp(&layout.city.get_price(*b)));
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if new_candidates.len() == 0 {
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//eprintln!("Did not find candidate");
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} else {
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for (i, &candidate) in new_candidates.iter().enumerate() {
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//eprint!("Found candidate {}...", i);
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//let old_price = layout.price();
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layout.remove_house(house_index);
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layout.add_house(candidate);
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assert!(layout.is_valid());
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//let new_price = layout.price();
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//let price_diff = new_price as i64 - old_price as i64;
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//eprintln!(" candidate is valid, price diff: {}.", price_diff);
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//eprintln!("Improved price: {}", new_price);
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improved = true;
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untried_houses = layout.houses().clone();
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untried_houses.shuffle(&mut rng);
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break;
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}
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}
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}
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improved
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}
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pub fn improve_merge_pairwise(layout: &mut HouseLayout, print_progress: bool) -> bool {
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let mut improved = false;
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loop {
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// This here is a hack for being unable to modify the houses while looping through them.
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// We instead go through the houses repeatedly and remember which pairs we have already
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// tried by hashing their values because they can and do move throughout the layout Vec
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// as it's being modified.
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// TODO: This may lead to some pairs still being mergeable thanks to another merge
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// that happened before.
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let mut checked = HashSet::new();
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let mut loop_improved = false;
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loop {
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let mut merge = None;
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'outer_houses: for i in 0..layout.houses().len() {
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for j in i + 1..layout.houses().len() {
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let house1 = layout.houses()[i];
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let house2 = layout.houses()[j];
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let x_dist = (house1.x as i32 - house2.x as i32).abs() as usize;
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let y_dist = (house1.y as i32 - house2.y as i32).abs() as usize;
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if x_dist > 4 * HOUSE_RANGE || y_dist > 4 * HOUSE_RANGE {
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// Never close enough to merge
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continue;
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}
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if checked.contains(&(house1, house2)) || checked.contains(&(house2, house1)) {
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continue;
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} else {
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checked.insert((house1, house2));
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}
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match get_valid_move_rectangle_multiple(&layout, &vec! {house1, house2}) {
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Ok(rect) => {
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let mut cheapest = None;
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for y in rect.top..=rect.bottom {
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for x in rect.left..=rect.right {
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if !layout.city.is_house_xy(x, y) { continue; }
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let price = layout.city.get_price_xy(x, y);
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match cheapest {
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None => cheapest = Some((x, y, price)),
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Some((_, _, cheapest_price)) if price < cheapest_price => cheapest = Some((x, y, price)),
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_ => {}
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};
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}
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}
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if let Some((x, y, price)) = cheapest {
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if price >= layout.city.get_price(house1) + layout.city.get_price(house2) {
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// Merging not worth
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//eprintln!("Merging not worth!");
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} else {
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merge = Some((i, j, House::new(x, y)));
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break 'outer_houses;
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}
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}
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}
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Err(RectangleSearchError::Useless) => {
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//eprintln!("Found useless pair of houses, not solving!")
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},
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Err(RectangleSearchError::Unsatisfiable) => {}
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}
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}
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}
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if let Some((i, j, house)) = merge {
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let old_price = layout.price();
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assert!(i < j);
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layout.remove_house(j);
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layout.remove_house(i);
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layout.add_house(house);
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assert!(layout.is_valid());
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let new_price = layout.price();
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let price_diff = new_price as i32 - old_price as i32;
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if print_progress {
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eprintln!("Merged two houses, new price {}, diff {}", new_price, price_diff);
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}
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improved = true;
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loop_improved = true;
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} else {
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break;
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}
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}
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if !loop_improved {
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break;
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}
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}
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improved
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}
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