add 538

Author: shishishu

README.md

@@ -31,4 +31,5 @@ Idx | Date | Question | Python| Java | Domain | Tag | Difficulty | Remark
 025|20200216|[2. Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)|[002p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/002_Add_Two_Numbers.ipynb)|[002j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/002/Solution.java)|List||Medium
 026|20200223|[530. Minimum Absolute Difference in BST](https://leetcode.com/problems/minimum-absolute-difference-in-bst/)|[530p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/530_Minimum_Absolute_Difference_in_BST.ipynb)|[530j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/530/Solution.java)|BST|Recursive|Easy
 027|20200301|[938. Range Sum of BST](https://leetcode.com/problems/range-sum-of-bst/)|[938p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/938_Range_Sum_of_BST.ipynb)|[938j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/938/Solution.java)|BST|Recursive/Iterative|Easy
-028|20200301|[450. Delete Node in a BST](https://leetcode.com/problems/delete-node-in-a-bst/)|[450p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/450_Delete_Node_in_a_BST.ipynb)|[450j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/450/Solution.java)|BST|Recursive|Medium
+028|20200301|[450. Delete Node in a BST](https://leetcode.com/problems/delete-node-in-a-bst/)|[450p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/450_Delete_Node_in_a_BST.ipynb)|[450j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/450/Solution.java)|BST|Recursive|Medium
+029|20200329|[538. Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/)|[538p](https://github.com/shishishu/leetcode-python-java/blob/master/ipynb_files/538_Convert_BST_to_Greater_Tree.ipynb)|[538j](https://github.com/shishishu/leetcode-python-java/blob/master/java_codes/538/Solution.java)|BST|Recursive/Iterative|Easy

images/538_Q.PNG

@@ -0,0 +1,49 @@
+import java.util.Stack;
+
+class TreeNode {
+    int val;
+    TreeNode left;
+    TreeNode right;
+    TreeNode(int x) {
+        val = x;
+    }
+}
+
+// traverse
+class Solution {
+
+    int total = 0;
+    public TreeNode convertBST(TreeNode root) {
+        visit(root);
+        return root;
+    }
+
+    public void visit(TreeNode root) {
+        if (root != null){
+            visit(root.right);
+            root.val += total;
+            total = root.val;
+            visit(root.left);
+        }
+    }
+}
+
+// iterative
+class Solution {
+    public TreeNode convertBST(TreeNode root) {
+        int total = 0;
+        TreeNode node = root;
+        Stack<TreeNode> stack = new Stack<>();
+        while (!stack.isEmpty() || node != null){
+            while (node != null){
+                stack.add(node);
+                node = node.right;
+            }
+            node = stack.pop();
+            total += node.val;
+            node.val = total;
+            node = node.left;
+        }
+        return root;
+    }
+}

images/538_S1.PNG

@@ -32,6 +32,7 @@
       <sourceFolder url="file://$MODULE_DIR$/530" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/938" isTestSource="false" />
       <sourceFolder url="file://$MODULE_DIR$/450" isTestSource="false" />
+      <sourceFolder url="file://$MODULE_DIR$/538" isTestSource="false" />
     </content>
     <orderEntry type="inheritedJdk" />
     <orderEntry type="sourceFolder" forTests="false" />