Compilare: user.cpp: In function ‘int main()’: user.cpp:98:18: warning: converting to non-pointer type ‘char’ from NULL [-Wconversion-null] sol[ans + 1] = NULL; ^ user.cpp:72:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("string.in", "r", stdin); ^ user.cpp:73:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("string.out", "w", stdout); ^ user.cpp:75:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:77:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s", s + 1); ^