diff --git a/src/my_project/interviews/google_top_exercises/round_1/22_diameter_binary_tree.py b/src/my_project/interviews/google_top_exercises/round_1/22_diameter_binary_tree.py
new file mode 100644
index 00000000..99888f3a
--- /dev/null
+++ b/src/my_project/interviews/google_top_exercises/round_1/22_diameter_binary_tree.py
@@ -0,0 +1,33 @@
+class TreeNode:
+    def __init__(self, val=0, left=None, right=None):
+        self.val = val
+        self.left = left
+        self.right = right
+        
+class Solution(object):
+    def diameterOfBinaryTree(self, root):
+        """
+        :type root: TreeNode
+        :rtype: int
+        """
+        self.diameter = 0
+
+        def depth(node):
+            """
+            Returns the height (in edges) of the subtree rooted at node.
+            Updates self.diameter with the longest path through this node.
+            """
+            if not node:
+                return -1
+
+            left_depth = depth(node.left)
+            right_depth = depth(node.right)
+
+            # Path through this node uses both subtrees: edges on each side
+            self.diameter = max(self.diameter, left_depth + right_depth + 2)
+
+            # Only one branch can be extended toward the parent
+            return max(left_depth, right_depth) + 1
+
+        depth(root)
+        return self.diameter
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