Compilare: user.cpp: In function ‘void doit(std::vector<std::pair<int, int> >&)’: user.cpp:93:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:162:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < color[0].size(); ++i) ^ user.cpp:164:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < color[0][i].size(); ++j) ^ user.cpp:170:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < color[0].size(); ++i) ^ user.cpp:178:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < color[i].size(); ++j) ^ user.cpp:184:48: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (connections == color[0].size()-1) ^ user.cpp:132:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("unlock.in", "r", stdin); ^ user.cpp:133:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("unlock.out", "w", stdout); ^