template <class InputerIterator,class RandomAccessIterator>
RandomAccessIterator random_sample(InputerIterator first,InputIterator last,RandomAccessIterator ofirst,RandomAccessIterator olast);
template <class InputerIterator,class RandomAccessIterator>
RandomAccessIterator random_sample(InputerIterator first,InputIterator last,RandomAccessIterator ofirst,RandomAccessIterator olast,RandomNumberGenerator &rand);
template <class InputerIterator,class OutputerIterator,class Distance>
OutputerIterator random_sample_n(InputerIterator first,InputIterator last,OutputerIterator out,Distance n);
template <class InputerIterator,class OutputerIterator,class Distance,class RandomNumberGenerator>
OutputerIterator random_sample_n(InputerIterator first,InputIterator last,OutputerIterator out,Distance n,RandomNumberGenerator &rand);