Compilare: user.cpp: In function ‘int main()’: user.cpp:20:16: warning: format ‘%s’ expects argument of type ‘char*’, but argument 2 has type ‘char (*)[500]’ [-Wformat=] scanf("%s", &s); ^ user.cpp:24:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < strlen(s); ++i) { ~~^~~~~~~~~~~ user.cpp:25:13: warning: array subscript has type ‘char’ [-Wchar-subscripts] cache[s[i]]++; ^ user.cpp:26:17: warning: array subscript has type ‘char’ [-Wchar-subscripts] if (cache[s[i]] == 2) { ^ user.cpp:13:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cod2.in", "r", stdin); ^ user.cpp:14:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("cod2.out", "w", stdout); ^ user.cpp:19:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &n); ^ user.cpp:20:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", &s); ^