Compilare: main.cpp: In function 'int main()': main.cpp:34:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(l[i] < a[i].size() && viz[a[i][l[i]]]) ~~~~~^~~~~~~~~~~~~ main.cpp:36:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(l[i] < a[i].size()) cnt[a[i][l[i]]]++; ~~~~~^~~~~~~~~~~~~