## Question

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 v and w as the lowest node in T that has both v and w as descendants (**where we allow a node to be a descendant of itself**).”

_______3______ / \ ___5__ ___1__ / \ / \ 6 _2 0 8 / \ 7 4

For example, the lowest common ancestor (LCA) of nodes `5`

and `1`

is `3`

. Another example is LCA of nodes `5`

and `4`

is `5`

, since a node can be a descendant of itself according to the LCA definition.

## Solution

**Result:** Accepted **Time:** 16 ms

Here should be some explanations.

```
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* struct TreeNode *left;
* struct TreeNode *right;
* };
*/
struct TreeNode* lowestCommonAncestor(struct TreeNode* root, struct TreeNode* p, struct TreeNode* q) {
if(!root || root == p || root == q)
return root;
struct TreeNode* left = lowestCommonAncestor(root->left, p, q);
struct TreeNode* right = lowestCommonAncestor(root->right, p, q);
if(left)
return right?root:left;
return right;
}
```

**Complexity Analytics**

- Time Complexity:
- Space Complexity: