Compilare: user.cpp: In function ‘int main()’: user.cpp:23:14: warning: array subscript has type ‘char’ [-Wchar-subscripts] app[c]++; ^ user.cpp:33:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (!used[c]) { ^ user.cpp:36:30: warning: array subscript has type ‘char’ [-Wchar-subscripts] app[st.back()] > 0 ^ user.cpp:38:31: warning: array subscript has type ‘char’ [-Wchar-subscripts] used[st.back()] = false; ^ user.cpp:42:19: warning: array subscript has type ‘char’ [-Wchar-subscripts] used[c] = true; ^ user.cpp:46:14: warning: array subscript has type ‘char’ [-Wchar-subscripts] app[c]--; ^ user.cpp:28:9: warning: unused variable ‘len’ [-Wunused-variable] int len = 0; ^ user.cpp:11:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("calandrinon.in", "r", stdin); ^ user.cpp:12:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("calandrinon.out", "w", stdout); ^ user.cpp:14:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int n; scanf("%d\n", &n); ^ user.cpp:19:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] char c; scanf("%c", &c); ^