Merge pull request #3267 from a1exanddrovich/0538-dev

Create: 0538-convert-bst-to-greater-tree.java

Author: a93a

java/0538-convert-bst-to-greater-tree.java

@@ -0,0 +1,43 @@
+// Recursive solution
+class Solution {
+    private int curSum = 0;
+
+    public TreeNode convertBST(TreeNode root) {
+         convertBSTRecursive(root);
+         return root;
+    }
+
+    private void convertBSTRecursive(TreeNode node) {
+        if (node == null) {
+            return;
+        }
+
+        convertBSTRecursive(node.right);
+        int temp = node.val;
+        node.val += curSum;
+        curSum += temp;
+        convertBSTRecursive(node.left);
+    }
+}
+
+// Iterative solution
+class Solution {
+    public TreeNode convertBST(TreeNode root) {
+        Stack<TreeNode> stack = new Stack<>();
+        TreeNode cur = root;
+
+        int curSum = 0;
+        while (cur != null || !stack.isEmpty()) {
+            while (cur != null) {
+                stack.push(cur);
+                cur = cur.right;
+            }
+            cur = stack.pop();
+            cur.val += curSum;
+            curSum = cur.val;
+            cur = cur.left;
+        }
+
+        return root;
+    }
+}