Update 0501.二叉搜索树中的众数.md

problems/0501.二叉搜索树中的众数.md

@@ -876,6 +876,55 @@ object Solution {
 }
 ```
 
+## rust
+
+递归：
+
+```rust
+impl Solution {
+    pub fn find_mode(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let mut count = 0;
+        let mut max_count = 0;
+        let mut res = vec![];
+        let mut pre = i32::MIN;
+        Self::search_bst(&root, &mut pre, &mut res, &mut count, &mut max_count);
+        res
+    }
+    pub fn search_bst(
+        cur: &Option<Rc<RefCell<TreeNode>>>,
+        mut pre: &mut i32,
+        res: &mut Vec<i32>,
+        count: &mut i32,
+        max_count: &mut i32,
+    ) {
+        if cur.is_none() {
+            return;
+        }
+
+        let cur_node = cur.as_ref().unwrap().borrow();
+        Self::search_bst(&cur_node.left, pre, res, count, max_count);
+        if *pre == i32::MIN {
+            *count = 1;
+        } else if *pre == cur_node.val {
+            *count += 1;
+        } else {
+            *count = 1;
+        };
+        match count.cmp(&max_count) {
+            std::cmp::Ordering::Equal => res.push(cur_node.val),
+            std::cmp::Ordering::Greater => {
+                *max_count = *count;
+                res.clear();
+                res.push(cur_node.val);
+            }
+            _ => {}
+        };
+        *pre = cur_node.val;
+        Self::search_bst(&cur_node.right, pre, res, count, max_count);
+    }
+}
+```
+
 
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