📝 docs : add 538. Convert BST to Greater Tree.md

Author: GoogTech

docs/LeetCod刷题之旅及题目解析/538.把二叉搜索树转换为累加树/538.把二叉搜索树转换为累加树.md

@@ -0,0 +1,99 @@
+## 538. 把二叉搜索树转换为累加树
+> https://leetcode-cn.com/problems/convert-bst-to-greater-tree/
+
+
+### Java
+```java
+/*
+ * @Author: Goog Tech
+ * @Date: 2020-08-16 12:23:26
+ * @LastEditTime: 2020-08-16 12:30:19
+ * @Description: https://leetcode-cn.com/problems/convert-bst-to-greater-tree/
+ * @FilePath: \leetcode-googtech\#538. Convert BST to Greater Tree\Solution.java
+ * @WebSite: https://algorithm.show/
+ */
+
+/*
+ * @lc app=leetcode.cn id=538 lang=java
+ *
+ * [538] 把二叉搜索树转换为累加树
+ */
+
+// @lc code=start
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+
+    private int sum = 0;
+
+    // 利用反序中序遍历解题,注: 二叉搜索树的左子树 < 根 < 右子树
+    public TreeNode convertBST(TreeNode root) {
+        if(root != null) {
+            // 遍历右子树
+            convertBST(root.right);
+            // 对遍历到的每个节点值进行累加,并将其结果赋值给当前节点的值
+            sum  = sum + root.val;
+            root.val = sum;
+            // 遍历左子树
+            convertBST(root.left);
+        }
+        return root;
+    }
+}
+// @lc code=end
+```
+
+### Python
+```python
+'''
+Author: Goog Tech
+Date: 2020-08-16 12:10:39
+LastEditTime: 2020-08-16 12:30:38
+Description: https://leetcode-cn.com/problems/convert-bst-to-greater-tree/
+FilePath: \leetcode-googtech\#538. Convert BST to Greater Tree\Solution.py
+WebSite: https://algorithm.show/
+'''
+#
+# @lc app=leetcode.cn id=538 lang=python
+#
+# [538] 把二叉搜索树转换为累加树
+#
+
+# @lc code=start
+# Definition for a binary tree node.
+# class TreeNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution(object):
+
+    def __init__(self):
+        self.total = 0
+
+    # 利用反序中序遍历解题,注: 二叉搜索树的左子树 < 根 <右子树
+    def convertBST(self, root):
+        """
+        :type root: TreeNode
+        :rtype: TreeNode
+        """
+        if root is not None:
+            # 遍历右子树
+            self.convertBST(root.right)
+            # 对遍历到的每个节点值进行累加,并将其结果赋值给当前节点的值
+            self.total = self.total + root.val
+            root.val = self.total
+            # 遍历左子树
+            self.convertBST(root.left)
+        return root
+
+# @lc code=end
+```

docs/SUMMARY.md

@@ -64,6 +64,7 @@
     * [434.字符串中的单词数](LeetCod刷题之旅及题目解析/434.字符串中的单词数/434.字符串中的单词数.md)
     * [485.最大连续1的个数](LeetCod刷题之旅及题目解析/485.最大连续1的个数/485.最大连续1的个数.md)
     * [520.检测大写字母](LeetCod刷题之旅及题目解析/520.检测大写字母/520.检测大写字母.md)
+    * [538.把二叉搜索树转换为累加树](LeetCod刷题之旅及题目解析/538.把二叉搜索树转换为累加树/538.把二叉搜索树转换为累加树.md)
     * [557.反转字符串中的单词III](LeetCod刷题之旅及题目解析/557.反转字符串中的单词III/557.反转字符串中的单词III.md)
     * [559.N叉树的最大深度](LeetCod刷题之旅及题目解析/559.N叉树的最大深度/559.N叉树的最大深度.md)
     * [561.数组拆分I](LeetCod刷题之旅及题目解析/561.数组拆分I/561.数组拆分I.md)