添加0530.二叉搜索树的最小绝对值差.md迭代Java解法

problems/0530.二叉搜索树的最小绝对差.md

@@ -171,7 +171,34 @@ class Solution {
     }
 }
 ```
+迭代法-中序遍历
 
+```java
+class Solution {
+    TreeNode pre;
+    Stack<TreeNode> stack;
+    public int getMinimumDifference(TreeNode root) {
+        if (root == null) return 0;
+        stack = new Stack<>();
+        TreeNode cur = root;
+        int result = Integer.MAX_VALUE;
+        while (cur != null || !stack.isEmpty()) {
+            if (cur != null) {
+                stack.push(cur);
+                cur = cur.left; // 左节点入栈
+            }else {
+                cur = stack.pop(); // 右节点入栈
+                if (pre != null) {
+                    result = Math.min(result, cur.val - pre.val);
+                }
+                pre = cur;
+                cur = cur.right;
+            }
+        }
+        return result;
+    }
+}
+```
 ## Python 
 
 递归