Merge pull request #1795 from fwqaaq/patch-7

Update 0501.二叉搜索树中的众数.md about rust

problems/0501.二叉搜索树中的众数.md

@@ -837,6 +837,93 @@ 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);
+    }
+}
+```
+
+迭代：
+
+```rust
+pub fn find_mode(root: Option<Rc<RefCell<TreeNode>>>) -> Vec<i32> {
+        let (mut cur, mut pre) = (root, i32::MIN);
+        let mut res = vec![];
+        let mut stack = vec![];
+        let (mut count, mut max_count) = (0, 0);
+        while !stack.is_empty() || cur.is_some() {
+            while let Some(node) = cur {
+                cur = node.borrow().left.clone();
+                stack.push(node);
+            }
+            if let Some(node) = stack.pop() {
+                if pre == i32::MIN {
+                    count = 1;
+                } else if pre == node.borrow().val {
+                    count += 1;
+                } else {
+                    count = 1;
+                }
+                match count.cmp(&max_count) {
+                    std::cmp::Ordering::Equal => res.push(node.borrow().val),
+                    std::cmp::Ordering::Greater => {
+                        max_count = count;
+                        res.clear();
+                        res.push(node.borrow().val);
+                    }
+                    _ => {}
+                }
+                pre = node.borrow().val;
+                cur = node.borrow().right.clone();
+            }
+        }
+        res
+    }
+```
+
 
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