> For the complete documentation index, see [llms.txt](https://gl01.gitbook.io/gfg-editorials/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl01.gitbook.io/gfg-editorials/2023/11-2023-nov-20/21-determine-if-two-trees-are-identical.md).

# 21. Determine if Two Trees are Identical

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/determine-if-two-trees-are-identical/1)

![](https://badgen.net/badge/Level/Easy/green)

## My Approach

To determine if two trees are identical, I recursively compare corresponding nodes in both trees. The base cases are:

* If both nodes are `NULL`, they are identical.
* If only one of the nodes is `NULL` or their data is not equal, they are not identical. Then, I recursively check the left and right subtrees for identity.

## Time and Auxiliary Space Complexity

* **Time Complexity** : `O(N)`, where `N` is the number of nodes in the tree.
* **Auxiliary Space Complexity** : `O(H)`, where `H` is the height of the tree.

## Code (C++)

```cpp
class Solution {
public:
    bool isIdentical(Node *r1, Node *r2) {
        if (!r1 && !r2) 
            return true;
        
        if (!r1 || !r2 || r1->data != r2->data) 
            return false;
        
        return isIdentical(r1->left, r2->left) && isIdentical(r1->right, r2->right);
    }
};
```

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