Compilare: main.cpp: In function 'void getFreq()': main.cpp:123:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.size(); i++) ~~^~~~~~~~~~ main.cpp: In function 'void read_buffer()': main.cpp:18:51: warning: ignoring return value of 'size_t fread(void*, size_t, size_t, FILE*)', declared with attribute warn_unused_result [-Wunused-result] fread(buffer, sizeof(char), BUFFER_SIZE, file); ^