Compilare: user.cpp: In function ‘void dfs(long int)’: user.cpp:18:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(long i = 0 ; i < adj_mat[s].size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:30:32: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%li %li", &N, &M); ^ user.cpp:37:34: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%li %li", &a , &b); ^