. - 力扣（LeetCode）

class Solution {
public:
    TreeNode* insertIntoBST(TreeNode* root, int val) {
        if (root == nullptr) {
            return new TreeNode(val);
        }
        TreeNode* pos = root;
        while (pos != nullptr) {
            if (val < pos->val) {
                if (pos->left == nullptr) {
                    pos->left = new TreeNode(val);
                    break;
                } else {
                    pos = pos->left;
                }
            } else {
                if (pos->right == nullptr) {
                    pos->right = new TreeNode(val);
                    break;
                } else {
                    pos = pos->right;
                }
            }
        }
        return root;
    }
};