Compilare: user.cpp: In function ‘int main()’: user.cpp:30:8: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[a] = 0; ^ user.cpp:31:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[b] = 1; ^ user.cpp:32:5: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[c] = 2; ^ user.cpp:41:32: warning: array subscript has type ‘char’ [-Wchar-subscripts] stk[++top] = v[s[i]]; ^ user.cpp:19:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cristale.in", "r", stdin); ^ user.cpp:20:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cristale.out", "w", stdout); ^