diff --git a/10 October LeetCode Challenge 2021/11_diameterOfTree.cpp b/10 October LeetCode Challenge 2021/11_diameterOfTree.cpp
new file mode 100644
index 0000000..cd134e4
--- /dev/null
+++ b/10 October LeetCode Challenge 2021/11_diameterOfTree.cpp	
@@ -0,0 +1,31 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    int height (TreeNode *root){
+        if (root == NULL)
+            return 0;
+        return 1 + max( height(root->left), height(root->right) );
+    }
+    
+    
+    int diameterOfBinaryTree(TreeNode* root) {
+        
+        if (root == NULL)
+            return 0;
+        
+        int d1 =  height (root -> left) + height (root -> right);
+        int d2 = diameterOfBinaryTree (root ->left);
+        int d3 = diameterOfBinaryTree (root -> right);
+        
+        return max(d1, max(d2, d3));
+        
+    }
+};