C++ 代码

/**
 * 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||p==root||q==root){
            return root;
        }
        auto left=lowestCommonAncestor( root->left,  p,  q); 
        auto right=lowestCommonAncestor( root->right,  p,  q); 
         if(!left){
             return right;
         }
         if(!right){
             return left;
         }
         return root;
    }
};