up03-3 (delete two vectors)

#include <vector>
#include <algorithm>

void process(const std::vector<int> &v1, std::vector<int> &v2)
{
    std::vector<int> v1_copy(v1);

    std::sort(v1_copy.begin(), v1_copy.end());

    auto valid_begin = v1_copy.begin();
    auto valid_end = std::unique(v1_copy.begin(), v1_copy.end());


    for (auto i = valid_begin; i != valid_end; i++) {
        if (*i < 0) {
            valid_begin = i + 1;
        } else if (size_t(*i) > v2.size()) {
            valid_end = i;
            break;
        }
    }
    if (valid_begin == valid_end) {
        return;
    }
    int counter = 0;
    auto j = valid_begin;

    for (auto i = v2.begin(); i != v2.end(); ++i) {
        if (j != valid_end && *j == std::distance(v2.begin(), i)) {
            ++j;
            ++counter;
            continue;
        }

        if (counter > 0) {
            std::swap(*(i), *(i - counter));
        }
    }
    v2.erase(v2.end() - counter, v2.end());
}