33-3-4/src/combine.rs

use crate::city;
use crate::city::{City, House, SIZE, HOUSE_RANGE};
use itertools::Itertools;
use std::collections::VecDeque;

pub fn try_combine(city: &City, layout1: &Vec<House>, layout2: &Vec<House>) {
    // Sorted in reverse so we can remove from the end
    let mut houses1_sorted: Vec<House> = layout1.iter().sorted_by(|h1, h2| h2.x.cmp(&h1.x)).map(|x| *x).collect();
    let mut houses2_sorted: Vec<House> = layout2.iter().sorted_by(|h1, h2| h2.x.cmp(&h1.x)).map(|x| *x).collect();

    // TODO: We may want to maintain K left sides and K right sides to compare K^2 layouts at once at each x

    // houses1 is left, houses2 is right

    let mut left = LeftLine::new();
    let mut right = RightLine::new();

    // Make sure that we include all houses initially
    while let Some(house) = houses2_sorted.pop() {
        right.add_house(house);
    }

    // x is the last left coordinate, x+1 is right
    for x in 0..SIZE {
        // Update the lines
        while let Some(house) = houses1_sorted.last() {
            if house.x == x {
                left.add_house(*house);
                houses1_sorted.pop();
            } else {
                break;
            }
        }
        right.remove_houses(x);

        // Check compatibility of lines
        if x == 0 {
            // Cannot check this due to limitations in the implementation of LeftLine,
            // it wouldn't be very interesting anyway.
            continue;
        }

        if is_compatible(city, &left, &right) {
            eprintln!("Compatible on X {}", x);
            let houses: Vec<_> = layout1.iter().filter(|h| h.x <= x).chain(layout2.iter().filter(|h| h.x > x)).map(|h| *h).collect();
            eprintln!("Price {}", city::get_price(&city, &houses));
            //if let Some(price) = city::is_valid(&city, &houses) {
            //    eprintln!("Merge valid with price {}", price)
            //} else {
            //    eprintln!("Merge actually invalid, printing invalid merge");
            //    println!("{}", houses.len());
            //    for house in houses {
            //        println!("{} {}", house.y, house.x);
            //    }
            //}
        } else {
            eprintln!("Incompatible on X {}", x);
        }
    }
}

fn is_compatible(city: &City, left: &LeftLine, right: &RightLine) -> bool {
    for y in 0..SIZE {
        let max_left_covered_x = left.get_max_covered_x(y);
        let min_right_covered_x = right.get_min_covered_x(y);

        // This range will often be empty
        for x in (max_left_covered_x+1)..min_right_covered_x {
            if city.is_house_xy(x, y) {
                // This is an uncovered house
                eprintln!("House ({},{}) in uncovered range [{},{}]", x, y, max_left_covered_x+1, min_right_covered_x-1);
                return false;
            }
        }
    }

    true
}

struct LeftLine {
    covers: Vec<usize>
}

struct RightLine {
    covers: Vec<usize>,
    houses: VecDeque<House>
}

impl LeftLine {
    pub fn new() -> Self {
        // XXX: Careful, default of 0 includes covering first vertical line
        let covers = vec![0; SIZE];
        LeftLine {covers}
    }

    pub fn add_house(&mut self, house: House) {
        let range_rect = house.range_rectangle();
        for y in range_rect.top..=range_rect.bottom {
            // Should always be the max variant
            self.covers[y] = self.covers[y].max(range_rect.right);
        }
    }

    pub fn get_max_covered_x(&self, y: usize) -> usize {
        self.covers[y]
    }
}

impl RightLine {
    pub fn new() -> Self {
        let covers = vec![usize::MAX; SIZE];
        let houses = VecDeque::new();
        RightLine {covers, houses}
    }

    pub fn add_house(&mut self, house: House) {
        // Added houses have to always be ordered by x
        eprintln!("Added house ({},{}) to right line", house.x, house.y);
        let range_rect = house.range_rectangle();
        for y in range_rect.top..=range_rect.bottom {
            self.covers[y] = self.covers[y].min(range_rect.left);
        }

        self.houses.push_back(house);
    }

    pub fn remove_houses(&mut self, x: usize) {
        // Has to be called with x, x+1, x+2...
        while let Some(house) = self.houses.front() {
            if house.x == x {
                let removed_house = self.houses.pop_front().unwrap();
                let removed_rect = removed_house.range_rectangle();

                // Remove the now-outdated distances around the removed house
                for y in removed_rect.top..=removed_rect.bottom {
                    self.covers[y] = usize::MAX;
                }

                // Update distances around the removed house if the area of any houses
                // intersects the removed area
                for house in &self.houses {
                    let house_rect = house.range_rectangle();
                    // TODO: Verify this intersection is correct
                    let y_intersection = if removed_house.y < house.y {
                        house_rect.top..=removed_rect.bottom
                    } else {
                        removed_rect.top..=house_rect.bottom
                    };

                    for y in y_intersection {
                        self.covers[y] = self.covers[y].min(house_rect.left);
                    }
                }
            } else {
                break;
            }
        }
    }

    pub fn get_min_covered_x(&self, y: usize) -> usize {
        self.covers[y].min(SIZE)
    }
}