Ch 4. Trees and Graphs / 4.2_Minimal_Tree.cpp syntax error

The code declares a pointer in line 10, but doesn't use pointer notation to access it

```cpp
TreeNode* newNode = new TreeNode(arr[mid]);
newNode.left = createMinBST(arr, start, mid - 1);  // Should be newNode->left
newNode.right = createMinBST(arr, mid + 1, end); // Should be newNode->right
```