Compilare: user.cpp: In function ‘void dfs(int, int)’: user.cpp:53:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph[node].size(); ++ i) ^ user.cpp: In function ‘void dfs2(int)’: user.cpp:97:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph[node].size(); ++ i) { ^ user.cpp:102:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j < graph[node].size() && found < 1; ++ j) ^ user.cpp:111:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (; j < graph[node].size() && found < 2; ++ j) ^ user.cpp:126:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph[node].size(); ++ i) ^ user.cpp:135:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph[node].size(); ++ i) { ^ user.cpp: In constructor ‘InputReader::InputReader(const char*)’: user.cpp:16:47: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In member function ‘void InputReader::advance()’: user.cpp:38:51: warning: ignoring return value of ‘size_t fread(void*, size_t, size_t, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fread(buffer, SIZE, 1, input_file); ^ user.cpp: In function ‘void dfs(int, int)’: user.cpp:72:36: warning: ‘pos_father’ may be used uninitialized in this function [-Wmaybe-uninitialized] swap(graph[node][pos_father], graph[node].back()); ^