Add problem 2353: Design a Food Rating System

Author: EFanZh

src/lib.rs

@@ -1744,6 +1744,7 @@ pub mod problem_2348_number_of_zero_filled_subarrays;
 pub mod problem_2349_design_a_number_container_system;
 pub mod problem_2351_first_letter_to_appear_twice;
 pub mod problem_2352_equal_row_and_column_pairs;
+pub mod problem_2353_design_a_food_rating_system;
 
 #[cfg(test)]
 mod test_utilities;

src/problem_2353_design_a_food_rating_system/binary_heap.rs

@@ -0,0 +1,246 @@
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+use std::cmp::Reverse;
+use std::collections::hash_map::Entry;
+use std::collections::HashMap;
+use std::convert;
+
+fn encode_name(name: &str) -> u64 {
+    let mut result = 0;
+    let mut offset = 64;
+
+    for c in name.bytes() {
+        offset -= 5;
+        result |= u64::from(c & 0b_11111) << offset;
+    }
+
+    result
+}
+
+fn decode_name(mut name: u64, buffer: String) -> String {
+    let mut result = buffer.into_bytes();
+
+    result.clear();
+
+    loop {
+        result.push((name >> 59) as u8 | 0b_0110_0000);
+
+        name <<= 5;
+
+        if name == 0 {
+            break;
+        }
+    }
+
+    String::from_utf8(result).unwrap()
+}
+
+fn get_stat(stats: &[(u32, u64, u16)], index: u16) -> (u32, Reverse<u64>) {
+    let (rating, food_name, _) = stats[usize::from(index)];
+
+    (rating, Reverse(food_name))
+}
+
+fn heap_sift_down(
+    heap: &mut [u16],
+    stats: &mut [(u32, u64, u16)],
+    stat_index: usize,
+    rating: u32,
+    food_name: u64,
+    mut heap_index: usize,
+) {
+    let stat = (rating, Reverse(food_name));
+
+    loop {
+        let left_child_heap_index = heap_index * 2 + 1;
+
+        if let Some(&left_child_stat_index) = heap.get(left_child_heap_index) {
+            let right_child_heap_index = left_child_heap_index + 1;
+
+            let child_heap_index = if let Some(&right_child_stat_index) = heap.get(right_child_heap_index) {
+                if get_stat(stats, right_child_stat_index) > get_stat(stats, left_child_stat_index) {
+                    right_child_heap_index
+                } else {
+                    left_child_heap_index
+                }
+            } else {
+                left_child_heap_index
+            };
+
+            let child_stat_index = heap[child_heap_index];
+
+            if get_stat(stats, child_stat_index) > stat {
+                heap[heap_index] = child_stat_index;
+                stats[usize::from(child_stat_index)].2 = heap_index as _;
+                heap_index = child_heap_index;
+            } else {
+                break;
+            }
+        } else {
+            break;
+        }
+    }
+
+    heap[heap_index] = stat_index as _;
+    stats[stat_index].2 = heap_index as _;
+}
+
+fn heap_sift_up(
+    heap: &mut [u16],
+    stats: &mut [(u32, u64, u16)],
+    stat_index: usize,
+    rating: u32,
+    food_name: u64,
+    mut heap_index: usize,
+) {
+    let stat = (rating, Reverse(food_name));
+
+    loop {
+        let parent_heap_index = heap_index.wrapping_sub(1) / 2;
+
+        if let Some(&parent_stat_index) = heap.get(parent_heap_index) {
+            let parent_stat = get_stat(stats, parent_stat_index);
+
+            if stat > parent_stat {
+                heap[heap_index] = parent_stat_index;
+                stats[usize::from(parent_stat_index)].2 = heap_index as _;
+                heap_index = parent_heap_index;
+            } else {
+                break;
+            }
+        } else {
+            break;
+        }
+    }
+
+    heap[heap_index] = stat_index as _;
+    stats[stat_index].2 = heap_index as _;
+}
+
+fn heap_build(heap: &mut Box<[u16]>, stats: &mut [(u32, u64, u16)]) {
+    let n = stats.len();
+
+    *heap = (0..n as _).collect();
+
+    for i in (0..n / 2).rev() {
+        let (rating, food_name, heap_index) = stats[i];
+
+        heap_sift_down(heap, stats, i, rating, food_name, usize::from(heap_index));
+    }
+}
+
+fn heap_update(heap: &mut [u16], stats: &mut [(u32, u64, u16)], stat_index: u16, rating: u32) {
+    let stat_index = usize::from(stat_index);
+    let stat = &mut stats[stat_index];
+
+    if rating != stat.0 {
+        let (old_rating, food_name, heap_index) = *stat;
+        let heap_index = usize::from(heap_index);
+
+        stat.0 = rating;
+
+        if rating < old_rating {
+            heap_sift_down(heap, stats, stat_index, rating, food_name, heap_index);
+        } else {
+            heap_sift_up(heap, stats, stat_index, rating, food_name, heap_index);
+        }
+    }
+}
+
+struct Ratings {
+    heap: Box<[u16]>,
+    stats: Vec<(u32, u64, u16)>,
+}
+
+pub struct FoodRatings {
+    food_to_cuisine: HashMap<u64, (u64, u16)>,
+    cuisine_ratings: HashMap<u64, Ratings>,
+}
+
+impl FoodRatings {
+    fn new(foods: Vec<String>, cuisines: Vec<String>, ratings: Vec<i32>) -> Self {
+        let mut food_to_cuisine = HashMap::new();
+        let mut cuisine_ratings = HashMap::<_, Ratings>::new();
+
+        foods
+            .into_iter()
+            .zip(cuisines)
+            .zip(ratings)
+            .for_each(|((food, cuisine), rating)| {
+                let food = encode_name(&convert::identity(food));
+                let cuisine = encode_name(&convert::identity(cuisine));
+
+                let stat_index = match cuisine_ratings.entry(cuisine) {
+                    Entry::Occupied(occupied_entry) => {
+                        let stats = &mut occupied_entry.into_mut().stats;
+                        let stat_index = stats.len() as _;
+
+                        stats.push((rating as _, food, stat_index));
+
+                        stat_index
+                    }
+                    Entry::Vacant(vacant_entry) => {
+                        vacant_entry.insert(Ratings {
+                            heap: Box::new([]),
+                            stats: vec![(rating as _, food, 0)],
+                        });
+
+                        0
+                    }
+                };
+
+                food_to_cuisine.insert(food, (cuisine, stat_index));
+            });
+
+        for ratings in cuisine_ratings.values_mut() {
+            heap_build(&mut ratings.heap, &mut ratings.stats);
+        }
+
+        Self {
+            food_to_cuisine,
+            cuisine_ratings,
+        }
+    }
+
+    fn change_rating(&mut self, food: String, new_rating: i32) {
+        let food = encode_name(&convert::identity(food));
+        let new_rating = new_rating as u32;
+        let (cuisine, stat_index) = self.food_to_cuisine[&food];
+        let ratings = self.cuisine_ratings.get_mut(&cuisine).unwrap();
+
+        heap_update(&mut ratings.heap, &mut ratings.stats, stat_index, new_rating);
+    }
+
+    fn highest_rated(&self, cuisine: String) -> String {
+        let encoded_cuisine = encode_name(&cuisine);
+        let ratings = &self.cuisine_ratings[&encoded_cuisine];
+        let stat_index = ratings.heap[0];
+        let food_name = ratings.stats[usize::from(stat_index)].1;
+
+        decode_name(food_name, cuisine)
+    }
+}
+
+// ------------------------------------------------------ snip ------------------------------------------------------ //
+
+impl super::FoodRatings for FoodRatings {
+    fn new(foods: Vec<String>, cuisines: Vec<String>, ratings: Vec<i32>) -> Self {
+        Self::new(foods, cuisines, ratings)
+    }
+
+    fn change_rating(&mut self, food: String, new_rating: i32) {
+        self.change_rating(food, new_rating);
+    }
+
+    fn highest_rated(&self, cuisine: String) -> String {
+        self.highest_rated(cuisine)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_solution() {
+        super::super::tests::run::<super::FoodRatings>();
+    }
+}

src/problem_2353_design_a_food_rating_system/mod.rs

@@ -0,0 +1,87 @@
+pub mod binary_heap;
+
+pub trait FoodRatings {
+    fn new(foods: Vec<String>, cuisines: Vec<String>, ratings: Vec<i32>) -> Self;
+    fn change_rating(&mut self, food: String, new_rating: i32);
+    fn highest_rated(&self, cuisine: String) -> String;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::FoodRatings;
+
+    enum Operation {
+        ChangeRating(&'static str, i32),
+        HighestRated(&'static str, &'static str),
+    }
+
+    pub fn run<F: FoodRatings>() {
+        let test_cases = [
+            (
+                (
+                    &["kimchi", "miso", "sushi", "moussaka", "ramen", "bulgogi"] as &[_],
+                    &["korean", "japanese", "japanese", "greek", "japanese", "korean"] as &[_],
+                    &[9, 12, 8, 15, 14, 7] as &[_],
+                ),
+                &[
+                    Operation::HighestRated("korean", "kimchi"),
+                    Operation::HighestRated("japanese", "ramen"),
+                    Operation::ChangeRating("sushi", 16),
+                    Operation::HighestRated("japanese", "sushi"),
+                    Operation::ChangeRating("ramen", 16),
+                    Operation::HighestRated("japanese", "ramen"),
+                ] as &[_],
+            ),
+            (
+                (
+                    &["emgqdbo", "jmvfxjohq", "qnvseohnoe", "yhptazyko", "ocqmvmwjq"],
+                    &["snaxol", "snaxol", "snaxol", "fajbervsj", "fajbervsj"],
+                    &[2, 6, 18, 6, 5],
+                ),
+                &[
+                    Operation::ChangeRating("qnvseohnoe", 11),
+                    Operation::HighestRated("fajbervsj", "yhptazyko"),
+                    Operation::ChangeRating("emgqdbo", 3),
+                    Operation::ChangeRating("jmvfxjohq", 9),
+                    Operation::ChangeRating("emgqdbo", 14),
+                    Operation::HighestRated("fajbervsj", "yhptazyko"),
+                    Operation::HighestRated("snaxol", "emgqdbo"),
+                ],
+            ),
+            (
+                (
+                    &["xucxenyckh", "rmzka", "kiesprtv"],
+                    &["oqinnmfsaf", "tgeb", "onzfzqjw"],
+                    &[8, 4, 3],
+                ),
+                &[
+                    Operation::ChangeRating("rmzka", 8),
+                    Operation::ChangeRating("rmzka", 8),
+                    Operation::ChangeRating("rmzka", 5),
+                    Operation::HighestRated("onzfzqjw", "kiesprtv"),
+                    Operation::HighestRated("oqinnmfsaf", "xucxenyckh"),
+                    Operation::HighestRated("onzfzqjw", "kiesprtv"),
+                ],
+            ),
+        ];
+
+        for ((foods, cuisines, ratings), operations) in test_cases {
+            let mut food_ratings = F::new(
+                foods.iter().copied().map(str::to_string).collect(),
+                cuisines.iter().copied().map(str::to_string).collect(),
+                ratings.to_vec(),
+            );
+
+            for operation in operations {
+                match *operation {
+                    Operation::ChangeRating(food, new_rating) => {
+                        food_ratings.change_rating(food.to_string(), new_rating);
+                    }
+                    Operation::HighestRated(cuisine, expected) => {
+                        assert_eq!(food_ratings.highest_rated(cuisine.to_string()), expected.to_string());
+                    }
+                }
+            }
+        }
+    }
+}