Compilare: main.cpp: In function 'int main()': main.cpp:16:18: warning: array subscript has type 'char' [-Wchar-subscripts] 16 | frecv[s[i]]++; | ~~~^ main.cpp:17:21: warning: array subscript has type 'char' [-Wchar-subscripts] 17 | if(frecv[s[i]]==1){ | ~~~^ main.cpp:20:29: warning: array subscript has type 'char' [-Wchar-subscripts] 20 | frecv[s[Back]]--; | ~~~~~~^ main.cpp:21:32: warning: array subscript has type 'char' [-Wchar-subscripts] 21 | if(frecv[s[Back]]==0) | ~~~~~~^