Compilare: main.cpp: In function 'int main()': main.cpp:19:18: warning: array subscript has type 'char' [-Wchar-subscripts] 19 | frec[s[i]] ++; | ^ main.cpp:34:22: warning: array subscript has type 'char' [-Wchar-subscripts] 34 | frec[s[i]]--; | ^ main.cpp:11:12: warning: unused variable 'i' [-Wunused-variable] 11 | int n, i, j, nr = 0, sum; | ^ main.cpp:11:15: warning: unused variable 'j' [-Wunused-variable] 11 | int n, i, j, nr = 0, sum; | ^