Create Solution.py

Author: PATILYASH007

solution/1000-1099/1028.Recover a Tree From Preorder Traversal/Solution.py

@@ -0,0 +1,39 @@
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+    def recoverFromPreorder(self, traversal: str) -> Optional[TreeNode]:
+        stack = []
+        depth = 0
+        num = 0
+        S = traversal
+        
+        i = 0
+        while i < len(S):
+            depth = 0
+            while i < len(S) and S[i] == '-':
+                depth += 1
+                i += 1
+
+            num = 0
+            while i < len(S) and S[i].isdigit():
+                num = num * 10 + int(S[i])
+                i += 1
+            
+            # Create the new node
+            newNode = TreeNode(num)
+
+            while len(stack) > depth:
+                stack.pop()
+
+            if stack:
+                if not stack[-1].left:
+                    stack[-1].left = newNode
+                else:
+                    stack[-1].right = newNode
+
+            stack.append(newNode)
+        return stack[0] if stack else None