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 == NULL)
            return NULL;
        
        if((root -> val == p -> val) || (root -> val == q -> val)){
            return root;
        }

        TreeNode* left = lowestCommonAncestor(root -> left, p, q);
        TreeNode* right = lowestCommonAncestor(root -> right, p, q);

        if(left && right)
        {
            return root;
        }
        else if(left == NULL && right){
            return right;
        }
        else if(left && right == NULL){
            return left;
        }
        else{
            return NULL;
        }

    }
};