Compilare: main.cpp: In function 'int main()': main.cpp:13:15: warning: array subscript has type 'char' [-Wchar-subscripts] 13 | fr[s[i]]++; | ~~~^ main.cpp:16:16: warning: iteration 25 invokes undefined behavior [-Waggressive-loop-optimizations] 16 | if(fr[i]==1) | ~~~~^ main.cpp:14:21: note: within this loop 14 | for(int i='a'; i<='z'; i++) | ~^~~~~