Create find_duplicate_subtrees.py

trees_and_graphs/find_duplicate_subtrees.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+# author: bt3gl
+#
+# Given the root of a binary tree, return all duplicate subtrees.
+#
+# 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
+
+
+def find_duplicates(root: Optional[TreeNode]) -> List[Optional[TreeNode]]:
+
+        result = []
+        counter = {}
+
+        def traverse(node):
+            if not node:
+                return ""
+
+            rep = ("(" + traverse(node.left) + ")" + \
+                            str(node.val) + "(" +  \
+                            traverse(node.right) + ")")
+            
+            if rep in counter:
+                counter[rep] += 1
+            else:
+                counter[rep] = 1
+
+            if counter[rep] == 2:
+                result.append(node)
+            
+            return rep
+        
+        traverse(root)
+        return result