Compilare: user.cpp: In function ‘void mergeSort(const std::vector<std::pair<int, int> >&, const std::vector<std::pair<int, int> >&)’: user.cpp:27:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < n && k1 < a.size() && k2 < b.size(); ++i) ^ user.cpp:27:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; i < n && k1 < a.size() && k2 < b.size(); ++i) ^ user.cpp:32:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (k1 < a.size()) ^ user.cpp:34:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (k2 < b.size()) ^ user.cpp: In function ‘int main()’: user.cpp:100:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < elem.size() - 1; ++i) ^ user.cpp:101:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i + 1; j < elem.size(); ++j) ^ user.cpp:103:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < elem.size(); ++i) ^