Update mergeable_heap.rs (#206)

rust/structures/mergeable_heap.rs

@@ -1,72 +1,88 @@
-use std::cell::RefCell;
-use std::mem::{replace, swap, take};
-use std::rc::Rc;
+use std::mem::swap;
 
 struct Heap<V> {
     value: V,
-    left: Option<Rc<RefCell<Heap<V>>>>,
-    right: Option<Rc<RefCell<Heap<V>>>>,
+    left: Option<Box<Heap<V>>>,
+    right: Option<Box<Heap<V>>>,
 }
 
-impl<V: PartialOrd + Clone> Heap<V> {
-    fn new(value: V) -> Option<Rc<RefCell<Heap<V>>>> {
-        Some(Rc::new(RefCell::new(Self {
+impl<V: PartialOrd> Heap<V> {
+    fn new(value: V) -> Option<Box<Heap<V>>> {
+        Some(Box::new(Self {
             value,
             left: None,
             right: None,
-        })))
+        }))
     }
-    fn merge<'a>(
-        mut a: &'a Option<Rc<RefCell<Heap<V>>>>,
-        mut b: &'a Option<Rc<RefCell<Heap<V>>>>,
-    ) -> Option<Rc<RefCell<Heap<V>>>> {
+
+    fn merge(a: Option<Box<Heap<V>>>, b: Option<Box<Heap<V>>>) -> Option<Box<Heap<V>>> {
         if a.is_none() {
-            return b.clone();
+            return b;
         }
         if b.is_none() {
-            return a.clone();
+            return a;
         }
-        if a.as_ref()?.borrow().value > b.as_ref()?.borrow().value {
-            swap(&mut a, &mut b);
+        let mut ra = a.unwrap();
+        let mut rb = b.unwrap();
+        if ra.value > rb.value {
+            swap(&mut ra, &mut rb);
         }
         if rand::random() {
-            let mut ra = a.as_ref()?.borrow_mut();
-            let l = take(&mut ra.left);
-            let r = take(&mut ra.right);
-            ra.left = r;
-            ra.right = l;
+            swap(&mut ra.left, &mut ra.right);
         }
-        let m = Self::merge(replace(&mut &a.as_ref()?.borrow_mut().left, &None), b);
-        a.as_ref()?.borrow_mut().left = m;
-        a.clone()
+        ra.left = Self::merge(ra.left, Some(rb));
+        Some(ra)
     }
 
-    fn remove_min(heap: &Option<Rc<RefCell<Heap<V>>>>) -> (Option<Rc<RefCell<Heap<V>>>>, V) {
-        let h = heap.as_ref().unwrap().borrow();
-        (Self::merge(&h.left, &h.right), h.value.clone())
+    fn remove_min(heap: Option<Box<Heap<V>>>) -> (Option<Box<Heap<V>>>, V) {
+        let h = heap.unwrap();
+        (Self::merge(h.left, h.right), h.value)
     }
 
-    fn add(heap: &Option<Rc<RefCell<Heap<V>>>>, value: V) -> Option<Rc<RefCell<Heap<V>>>> {
-        Self::merge(heap, &Heap::new(value))
+    fn add(heap: Option<Box<Heap<V>>>, value: V) -> Option<Box<Heap<V>>> {
+        Self::merge(heap, Heap::new(value))
     }
 }
 
 #[cfg(test)]
 mod tests {
     use crate::structures::mergeable_heap::Heap;
+    use rand::seq::SliceRandom;
+    use rand::thread_rng;
+    use rstest::rstest;
+
+    #[rstest]
+    #[case(&mut [])]
+    #[case(&mut [0])]
+    #[case(&mut [1, 1])]
+    #[case(&mut [3, 1, 2])]
+    fn basic_test(#[case] seq: &mut [u32]) {
+        test(seq);
+    }
+
+    #[test]
+    fn big_test1() {
+        let mut values = (0..10_000).collect::<Vec<u32>>();
+        values.shuffle(&mut thread_rng());
+        test(&mut values);
+    }
 
     #[test]
-    fn basic_test() {
-        let mut h = None;
-        h = Heap::add(&h, 3);
-        h = Heap::add(&h, 1);
-        h = Heap::add(&h, 2);
-        let mut values = Vec::new();
-        while h.is_some() {
-            let (heap, min_value) = Heap::remove_min(&h);
-            values.push(min_value);
-            h = heap;
+    fn big_test2() {
+        let mut values = vec![0; 10_000];
+        values.shuffle(&mut thread_rng());
+        test(&mut values);
+    }
+
+    fn test(seq: &mut [u32]) {
+        let mut heap = seq.iter().fold(None, |h, v| Heap::add(h, v));
+        let mut heap_sorted_values = Vec::new();
+        while heap.is_some() {
+            let (updated_heap, min_value) = Heap::remove_min(heap);
+            heap = updated_heap;
+            heap_sorted_values.push(*min_value);
         }
-        assert_eq!(values, [1, 2, 3]);
+        seq.sort();
+        assert_eq!(heap_sorted_values, seq);
     }
 }