Compilare: user.cpp: In function ‘int main()’: user.cpp:158:21: warning: NULL used in arithmetic [-Wpointer-arith] while(x[a]!=NULL) ^ user.cpp:128:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apel.in","r",stdin); ^ user.cpp:129:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("apel.out","w",stdout); ^ user.cpp:132:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(S); ^ user.cpp:155:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(x); ^ user.cpp:168:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(x); ^ /tmp/ccvhgOTf.o: In function `main': user.cpp:(.text.startup+0x6d): warning: the `gets' function is dangerous and should not be used.