chhaya12
diff --git a/‎Easy/Convert BST to Greater Tree.java
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Lines changed: 36 additions & 0 deletions
diff --git a/‎Easy/Convert BST to greater tree.java
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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+  public TreeNode convertBST(TreeNode root) {
+    Stack<TreeNode> stack = new Stack<>();
+    addToStack(stack, root);
+    int currSum = 0;
+    while (!stack.isEmpty()) {
+      TreeNode removed = stack.pop();
+      currSum += removed.val;
+      removed.val = currSum;
+      addToStack(stack, removed.left);
+    }
+    return root;
+  }
+  
+  private void addToStack(Stack<TreeNode> stack, TreeNode node) {
+    while (node != null) {
+      stack.push(node);
+      node = node.right;
+    }
+  }
+}