题目：

题解：

class Solution {
public:TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {TreeNode* ancestor = root;while (true) {if (p->val < ancestor->val && q->val < ancestor->val) {ancestor = ancestor->left;}else if (p->val > ancestor->val && q->val > ancestor->val) {ancestor = ancestor->right;}else {break;}}return ancestor;}
};