Compilare: main.cpp: In function 'int main()': main.cpp:71:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j = 0; j<v[i].size(); j++) ~^~~~~~~~~~~~ main.cpp: In function 'char next()': main.cpp:18:35: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buff, 1, bsize, fin); ^