20240321 Finished

src/problem/mod.rs

@@ -80,3 +80,4 @@ mod p310_minimum_height_trees;
 mod p303_range_sum_query_immutable;
 mod p1793_maximum_score_of_a_good_subarray;
 mod p1969_minimum_non_zero_product_of_the_array_elements;
+mod p2671_frequency_tracker;

src/problem/p2671_frequency_tracker.rs

@@ -0,0 +1,104 @@
+/**
+ * [2671] Frequency Tracker
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+use std::collections::{HashMap, HashSet};
+
+struct FrequencyTracker {
+    number_map : HashMap<i32, i32>,
+    frequency_map : HashMap<i32, HashSet<i32>>,
+}
+
+
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl FrequencyTracker {
+
+    fn new() -> Self {
+        FrequencyTracker {
+            number_map: HashMap::new(),
+            frequency_map: HashMap::new(),
+        }
+    }
+    
+    fn add(&mut self, number: i32) {
+        let mut entry = self.number_map.entry(number).or_insert(0);
+
+        if *entry != 0 {
+            if let Some(set) = self.frequency_map.get_mut(&entry) {
+                set.remove(&number);
+            }
+        }
+
+        *entry += 1;
+        let set = self.frequency_map.entry(*entry)
+            .or_insert(HashSet::new());
+        set.insert(number);
+    }
+    
+    fn delete_one(&mut self, number: i32) {
+        if let Some(entry) = self.number_map.get_mut(&number) {
+            if *entry == 0 {
+                return;
+            }
+
+            if let Some(set) = self.frequency_map.get_mut(&entry) {
+                set.remove(&number);
+            }
+
+            *entry -= 1;
+            let set = self.frequency_map.entry(*entry)
+                .or_insert(HashSet::new());
+            set.insert(number);
+        } 
+    }
+    
+    fn has_frequency(&self, frequency: i32) -> bool {
+        let set = self.frequency_map.get(&frequency);
+
+        match set {
+            Some(set) => set.len() != 0,
+            None => false
+        }
+    }
+}
+
+/**
+ * Your FrequencyTracker object will be instantiated and called as such:
+ * let obj = FrequencyTracker::new();
+ * obj.add(number);
+ * obj.delete_one(number);
+ * let ret_3: bool = obj.has_frequency(frequency);
+ */
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2671() {
+        let mut tracker = FrequencyTracker::new();
+
+        tracker.add(10);
+        tracker.delete_one(5);
+        assert!(tracker.has_frequency(1));
+        tracker.delete_one(10);
+        tracker.delete_one(9);
+        tracker.delete_one(10);
+        assert!(!tracker.has_frequency(1));
+        tracker.add(4);
+        assert!(tracker.has_frequency(1));
+        tracker.delete_one(4);
+        assert!(!tracker.has_frequency(1));
+        assert!(!tracker.has_frequency(1));
+        tracker.add(10);
+        assert!(tracker.has_frequency(1));
+    }
+}