# LeetCode 100. Same Tree

## Description

https://leetcode.com/problems/same-tree/

Given the roots of two binary trees `p` and `q`, write a function to check if they are the same or not.

Two binary trees are considered the same if they are structurally identical, and the nodes have the same value.

Example 1:

```Input: p = [1,2,3], q = [1,2,3]
Output: true
```

Example 2:

```Input: p = [1,2], q = [1,null,2]
Output: false
```

Example 3:

```Input: p = [1,2,1], q = [1,1,2]
Output: false
```

Constraints:

• The number of nodes in both trees is in the range `[0, 100]`.
• `-104 <= Node.val <= 104`

## Explanation

Our goal is to implement isSameTree(TreeNode p, TreeNode q) function.

There are two scenarios for isSameTree(TreeNode p, TreeNode q) to return true:

1. p and q are both null
2. when p and q aren’t null, p and q should have same value and p’s left and right subtrees should be same as q’s left and q.right subtrees.

## Java Solution

``````/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean isSameTree(TreeNode p, TreeNode q) {
if (p == null && q == null) {
return true;
}

if (p != null && q != null) {
if (p.val == q.val && isSameTree(p.left, q.left) && isSameTree(p.right, q.right)) {
return true;
}
}

return false;
}
}``````

## Python Solution

``````# 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
class Solution:
def isSameTree(self, p: TreeNode, q: TreeNode) -> bool:

return self.helper(p, q)

def helper(self, p, q):
if not p and not q:
return True

if not p or not q:
return False

if p.val != q.val:
return False

return self.helper(p.left, q.left) and self.helper(p.right, q.right)``````
• Time Complexity: O(N)
• Space Complexity: O(logN)