Update 0530.二叉搜索树的最小绝对差.md

Author: fwqaaq

problems/0530.二叉搜索树的最小绝对差.md

@@ -576,6 +576,38 @@ impl Solution {
 }
 ```
 
+迭代
+
+```rust
+impl Solution {
+    pub fn get_minimum_difference(mut root: Option<Rc<RefCell<TreeNode>>>) -> i32 {
+        if root.is_none() {
+            return 0;
+        }
+        let mut stack = vec![];
+        let mut pre = -1;
+        let mut res = i32::MAX;
+        while root.is_some() || !stack.is_empty() {
+            while let Some(node) = root {
+                root = node.borrow().left.clone();
+                stack.push(node);
+            }
+
+            let node = stack.pop().unwrap();
+
+            if pre >= 0 {
+                res = res.min(node.borrow().val - pre);
+            }
+
+            pre = node.borrow().val;
+
+            root = node.borrow().right.clone();
+        }
+        res
+    }
+}
+```
+
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