Compilare: user.cpp: In function ‘void add(hd)’: user.cpp:32:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < v.size() ; i++) ^ user.cpp: In function ‘int grad(char*)’: user.cpp:48:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < strlen(s) ; i++) ^ user.cpp:81:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < v.size() ; i++) ^ user.cpp: In function ‘int main()’: user.cpp:94:5: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(s); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:94:5: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(s); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:94:11: warning: ‘char* gets(char*)’ is deprecated [-Wdeprecated-declarations] gets(s); ^ In file included from /usr/include/c++/5/cstdio:42:0, from user.cpp:1: /usr/include/stdio.h:638:14: note: declared here extern char *gets (char *__s) __wur __attribute_deprecated__; ^ user.cpp:91:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grad.in","r",stdin); ^ user.cpp:92:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("grad.out","w",stdout); ^ user.cpp:94:12: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccWW8MOO.o: In function `main': user.cpp:(.text.startup+0x50): warning: the `gets' function is dangerous and should not be used.