STL源码剖析之算法：set_difference & set_symmetric_difference

template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_difference(InputIterator1 first1, InputIterator1 last1,
                                InputIterator2 first2, InputIterator2 last2,
                                OutputIterator result) {
    while(first1 != last1 && first2 != last2) {
        if(*first1 < *first2) {
            *result = *first1;
            ++first1;
            ++result;
        } else if(*first2 < *first1) {
            ++first2;
        } else {
            ++first1;
            ++first2;
        }
    }

    return copy(first1, last1, result);
}

 

template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator Set_symmetric_difference(InputIterator1 first1, InputIterator1 last1,
                                        InputIterator2 first2, InputIterator2 last2,
                                        OutputIterator result) {
    while(first1 != last1 && first2 != last2) {
        if(*first1 < *first2) {
            *result = *first1;
            ++first1;
            ++result;
        } else if(*first2 < *first1) {
            *result = *first2;
            ++first2;
            ++result;
        } else {
            ++first1;
            ++first2;
        }
    }

    return copy(first2, last2, copy(first1, last1, result));
}