1 class Solution {2 public:3     TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {4         if(root->val >= p->val && root->val <= q->val || root->val >= q->val && root->val <= p->val) return root;5         if(root->val > p->val) return lowestCommonAncestor(root->left, p, q);6         return lowestCommonAncestor(root->right, p, q);7     }8 };

 注意等号，因为root可能等于p或q。