In this post, we are going to solve the** 236. Lowest Common Ancestor of a Binary Tree** problem of Leetcode. This problem **236. Lowest Common Ancestor of a Binary Tree** is a Leetcode **medium **level problem. Let’s see the code, **236. Lowest Common Ancestor of a Binary Tree** **– Leetcode Solution**.

**Problem**

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes `p`

and `q`

as the lowest node in `T`

that has both `p`

and `q`

as descendants (where we allow **a node to be a descendant of itself**).”

**Example 1 :**

```
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 1
Output: 3
Explanation: The LCA of nodes 5 and 1 is 3.
```

**Example 2 :**

```
Input: root = [3,5,1,6,2,0,8,null,null,7,4], p = 5, q = 4
Output: 5
Explanation: The LCA of nodes 5 and 4 is 5, since a node can be a descendant of itself according to the LCA definition.
```

**Example 3 :**

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

**Constraints**

- The number of nodes in the tree is in the range
`[2, 10`

.^{5}] `-10`

^{9}<= Node.val <= 10^{9}- All
`Node.val`

are**unique**. `p != q`

`p`

and`q`

will exist in the tree.

Now, let’s see the code of **236. Lowest Common Ancestor of a Binary Tree** – Leetcode Solution.

**Lowest Common Ancestor of a Binary Tree – Leetcode Solution**

**Lowest Common Ancestor of a Binary Tree – Leetcode Solution**

**236. Lowest Common Ancestor of a Binary Tree** – Solution in Java

**– Solution in Java**

**236. Lowest Common Ancestor of a Binary Tree**/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) { if(root == null || root == p || root == q) return root; TreeNode left = lowestCommonAncestor(root.left,p,q); TreeNode right = lowestCommonAncestor(root.right,p,q); if(left == null){ return right; } else if(right == null){ return left; }else{ return root; } } }

**236. Lowest Common Ancestor of a Binary Tree** – Solution in C++

**C++**

**– Solution in****236. Lowest Common Ancestor of a Binary Tree**/** * 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: TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) { if (!root || root == p || root == q) return root; TreeNode* left = lowestCommonAncestor(root->left, p, q); TreeNode* right = lowestCommonAncestor(root->right, p, q); return !left ? right : !right ? left : root; } };

**236. Lowest Common Ancestor of a Binary Tree** **– Solution in **Python

**236. Lowest Common Ancestor of a Binary Tree****Python**

**– Solution in**# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution(object): def lowestCommonAncestor(self, root, p, q): if root in (None, p, q): return root left, right = (self.lowestCommonAncestor(kid, p, q) for kid in (root.left, root.right)) return root if left and right else left or right

**Note:** This problem **236. Lowest Common Ancestor of a Binary Tree** is generated by **Leetcode **but the solution is provided by **CodingBroz**. This tutorial is only for **Educational** and **Learning** purpose.