update rust heap (#1761)

Author: rongyi

codes/rust/chapter_heap/heap.rs

@@ -6,18 +6,28 @@
 
 use hello_algo_rust::include::print_util;
 
-use std::collections::BinaryHeap;
+use std::{cmp::Reverse, collections::BinaryHeap};
 
-fn test_push(heap: &mut BinaryHeap<i32>, val: i32, flag: i32) {
-    heap.push(flag * val); // 元素入堆
+fn test_push_max(heap: &mut BinaryHeap<i32>, val: i32) {
+    heap.push(val); // 元素入堆
     println!("\n元素 {} 入堆后", val);
-    print_util::print_heap(heap.iter().map(|&val| flag * val).collect());
+    print_util::print_heap(heap.iter().map(|&val| val).collect());
+}
+fn test_push_min(heap: &mut BinaryHeap<Reverse<i32>>, val: i32) {
+    heap.push(Reverse(val)); // 元素入堆
+    println!("\n元素 {} 入堆后", val);
+    print_util::print_heap(heap.iter().map(|&val| val.0).collect());
 }
 
-fn test_pop(heap: &mut BinaryHeap<i32>, flag: i32) {
+fn test_pop_max(heap: &mut BinaryHeap<i32>) {
     let val = heap.pop().unwrap();
-    println!("\n堆顶元素 {} 出堆后", flag * val);
-    print_util::print_heap(heap.iter().map(|&val| flag * val).collect());
+    println!("\n堆顶元素 {} 出堆后", val);
+    print_util::print_heap(heap.iter().map(|&val| val).collect());
+}
+fn test_pop_min(heap: &mut BinaryHeap<Reverse<i32>>) {
+    let val = heap.pop().unwrap().0;
+    println!("\n堆顶元素 {} 出堆后", val);
+    print_util::print_heap(heap.iter().map(|&val| val.0).collect());
 }
 
 /* Driver Code */
@@ -26,31 +36,29 @@ fn main() {
     // 初始化小顶堆
     #[allow(unused_assignments)]
     let mut min_heap = BinaryHeap::new();
-    // Rust 的 BinaryHeap 是大顶堆，当入队时将元素值乘以 -1 将其反转，当出队时将元素值乘以 -1 将其还原
-    let min_heap_flag = -1;
+    // Rust 的 BinaryHeap 是大顶堆，小顶堆一般会“套上”Reverse
     // 初始化大顶堆
     let mut max_heap = BinaryHeap::new();
-    let max_heap_flag = 1;
 
     println!("\n以下测试样例为大顶堆");
 
     /* 元素入堆 */
-    test_push(&mut max_heap, 1, max_heap_flag);
-    test_push(&mut max_heap, 3, max_heap_flag);
-    test_push(&mut max_heap, 2, max_heap_flag);
-    test_push(&mut max_heap, 5, max_heap_flag);
-    test_push(&mut max_heap, 4, max_heap_flag);
+    test_push_max(&mut max_heap, 1);
+    test_push_max(&mut max_heap, 3);
+    test_push_max(&mut max_heap, 2);
+    test_push_max(&mut max_heap, 5);
+    test_push_max(&mut max_heap, 4);
 
     /* 获取堆顶元素 */
-    let peek = max_heap.peek().unwrap() * max_heap_flag;
+    let peek = max_heap.peek().unwrap();
     println!("\n堆顶元素为 {}", peek);
 
     /* 堆顶元素出堆 */
-    test_pop(&mut max_heap, max_heap_flag);
-    test_pop(&mut max_heap, max_heap_flag);
-    test_pop(&mut max_heap, max_heap_flag);
-    test_pop(&mut max_heap, max_heap_flag);
-    test_pop(&mut max_heap, max_heap_flag);
+    test_pop_max(&mut max_heap);
+    test_pop_max(&mut max_heap);
+    test_pop_max(&mut max_heap);
+    test_pop_max(&mut max_heap);
+    test_pop_max(&mut max_heap);
 
     /* 获取堆大小 */
     let size = max_heap.len();
@@ -65,9 +73,9 @@ fn main() {
     min_heap = BinaryHeap::from(
         vec![1, 3, 2, 5, 4]
             .into_iter()
-            .map(|val| min_heap_flag * val)
-            .collect::<Vec<i32>>(),
+            .map(|val| Reverse(val))
+            .collect::<Vec<Reverse<i32>>>(),
     );
     println!("\n输入列表并建立小顶堆后");
-    print_util::print_heap(min_heap.iter().map(|&val| min_heap_flag * val).collect());
+    print_util::print_heap(min_heap.iter().map(|&val| val.0).collect());
 }