simplify heap.rs and follow best practices (rust-lang#398)

Author: merelymyself

src/data_structures/heap.rs

@@ -88,12 +88,12 @@ where
     T: Default + Ord,
 {
     /// Create a new MinHeap
-    pub fn new_min() -> Self {
+    pub fn new_min() -> Heap<T> {
         Self::new(|a, b| a < b)
     }
 
     /// Create a new MaxHeap
-    pub fn new_max() -> Self {
+    pub fn new_max() -> Heap<T> {
         Self::new(|a, b| a > b)
     }
 }
@@ -130,42 +130,18 @@ where
     }
 }
 
-pub struct MinHeap;
-
-impl MinHeap {
-    #[allow(clippy::new_ret_no_self)]
-    pub fn new<T>() -> Heap<T>
-    where
-        T: Default + Ord,
-    {
-        Heap::new(|a, b| a < b)
-    }
-}
-
-pub struct MaxHeap;
-
-impl MaxHeap {
-    #[allow(clippy::new_ret_no_self)]
-    pub fn new<T>() -> Heap<T>
-    where
-        T: Default + Ord,
-    {
-        Heap::new(|a, b| a > b)
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
     #[test]
     fn test_empty_heap() {
-        let mut heap = MaxHeap::new::<i32>();
+        let mut heap: Heap<i32> = Heap::new_max();
         assert_eq!(heap.next(), None);
     }
 
     #[test]
     fn test_min_heap() {
-        let mut heap = MinHeap::new();
+        let mut heap = Heap::new_min();
         heap.add(4);
         heap.add(2);
         heap.add(9);
@@ -180,7 +156,7 @@ mod tests {
 
     #[test]
     fn test_max_heap() {
-        let mut heap = MaxHeap::new();
+        let mut heap = Heap::new_max();
         heap.add(4);
         heap.add(2);
         heap.add(9);

src/data_structures/mod.rs

@@ -18,7 +18,7 @@ pub use self::binary_search_tree::BinarySearchTree;
 pub use self::fenwick_tree::FenwickTree;
 pub use self::graph::DirectedGraph;
 pub use self::graph::UndirectedGraph;
-pub use self::heap::{Heap, MaxHeap, MinHeap};
+pub use self::heap::Heap;
 pub use self::linked_list::LinkedList;
 pub use self::queue::Queue;
 pub use self::rb_tree::RBTree;

src/searching/kth_smallest_heap.rs

@@ -1,4 +1,4 @@
-use crate::data_structures::MaxHeap;
+use crate::data_structures::Heap;
 use std::cmp::{Ord, Ordering};
 
 /// Returns k-th smallest element of an array.
@@ -28,7 +28,7 @@ where
     // than it
     // otherwise, E_large cannot be the kth smallest, and should
     // be removed from the heap and E_new should be added
-    let mut heap = MaxHeap::new();
+    let mut heap = Heap::new_max();
 
     // first k elements goes to the heap as the baseline
     for &val in input.iter().take(k) {