新增java 統一迭代法-中序遍历

新增java 統一迭代法-中序遍历

problems/0530.二叉搜索树的最小绝对差.md

@@ -174,6 +174,39 @@ class Solution {
     }
 }
 ```
+統一迭代法-中序遍历
+```Java
+class Solution {
+    public int getMinimumDifference(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode pre = null;
+        int result = Integer.MAX_VALUE;
+
+        if(root != null)
+            stack.add(root);
+        while(!stack.isEmpty()){
+            TreeNode curr = stack.peek();
+            if(curr != null){
+                stack.pop();
+                if(curr.right != null)
+                    stack.add(curr.right);
+                stack.add(curr);
+                stack.add(null);
+                if(curr.left != null)
+                    stack.add(curr.left);
+            }else{
+                stack.pop();
+                TreeNode temp = stack.pop();
+                if(pre != null)
+                    result = Math.min(result, temp.val - pre.val);
+                pre = temp;
+            }
+        }
+        return result;
+    }
+}
+```
+
 迭代法-中序遍历
 
 ```java