如何释放vector变量

std::vector<cv::Point> probp;
std::vector<int> plabel;

plabel.clear();
std::vector<int>().swap(plabel);
probp.clear();
std::vector<cv::Point>().swap(probp);

std::vector<cv::Point> probp;
std::vector<int> plabel;

plabel.clear();
std::vector<int>().swap(plabel);
probp.clear();
std::vector<cv::Point>().swap(probp);