Compilare: main.cpp: In function 'bool solve(std::vector<int>, int)': main.cpp:11:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < vec.size(); ++i) { ~~^~~~~~~~~~~~ main.cpp:12:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i + 1; j < vec.size(); ++j) { ~~^~~~~~~~~~~~ main.cpp:16:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < vec.size(); ++k) ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:27:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.in", "r", stdin); ^ main.cpp:28:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("bigfour.out", "w", stdout); ^