Compilare: user.cpp: In function ‘void dfs_plus(int)’: user.cpp:23:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<v[k].size();i++) ^ user.cpp: In function ‘void dfs_minus(int)’: user.cpp:33:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<g[k].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:77:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<sol.size();++i) ^ user.cpp:78:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<sol[i].size();++j) ^ user.cpp:79:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] cout<<sol[i][j]<<" \n"[j==sol[i].size()-1]; ^ user.cpp:55:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.in", "r", stdin); ^ user.cpp:56:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.out", "w", stdout); ^