Compilare: user.cpp: In function ‘int main()’: user.cpp:37:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (i=0; i<s.length(); i++) fq[s[i]]=i; ^ user.cpp:37:41: warning: array subscript has type ‘char’ [-Wchar-subscripts] for (i=0; i<s.length(); i++) fq[s[i]]=i; ^ user.cpp:41:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=0; j<s.length(); j++) ^ user.cpp:42:31: warning: array subscript has type ‘char’ [-Wchar-subscripts] tab[++poz]=fq[s[j]]; ^