Compilare: user.cpp: In function ‘int main()’: user.cpp:63:18: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] if(s[i]>='a' && s[i]<='z' || s[i]>='0' && s[i]<='9') ^ user.cpp:68:11: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] s[loc]=NULL; ^ user.cpp:80:15: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] cuv[j]=NULL; ^