题目：

题解：

struct TreeNode* lowestCommonAncestor(struct TreeNode* root, struct TreeNode* p, struct TreeNode* q) {struct 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;
}