first commit

problems/0538.把二叉搜索树转换为累加树.md

@@ -173,7 +173,23 @@ public:
 
 
 Java：
+```java
+class Solution {
+    private int count = 0;
+    public TreeNode convertBST(TreeNode root) {
+        convert(root);
+        return root;
+    }
 
+    private void convert (TreeNode root) {
+        if (root == null) return;
+        convert(root.right);
+        count += root.val;
+        root.val = count;
+        convert(root.left);
+    }
+}
+```
 
 Python：
 
@@ -187,4 +203,4 @@ Go：
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)
 * 知识星球：[代码随想录](https://mp.weixin.qq.com/s/QVF6upVMSbgvZy8lHZS3CQ)
-<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>
+<div align="center"><img src=../pics/公众号.png width=450 alt=> </img></div>