Compilare: user.cpp: In function ‘int main()’: user.cpp:25:21: warning: unused variable ‘m’ [-Wunused-variable] int n,i,j,k=0,t,m,t2,x,l; ^ user.cpp:25:26: warning: unused variable ‘x’ [-Wunused-variable] int n,i,j,k=0,t,m,t2,x,l; ^ user.cpp:22:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.in","r",stdin); ^ user.cpp:23:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("dictree.out", "w", stdout); ^ user.cpp:27:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); gets(a[0]); ^ user.cpp:27:31: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); gets(a[0]); ^ user.cpp:29:19: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(a[i]); ^ In file included from /usr/include/stdio.h:934:0, from /usr/include/c++/4.8/cstdio:42, from user.cpp:1: In function ‘char* gets(char*)’, inlined from ‘int main()’ at user.cpp:29:19: /usr/include/i386-linux-gnu/bits/stdio2.h:230:28: warning: call to ‘__gets_warn’ declared with attribute warning: please use fgets or getline instead, gets can't specify buffer size [enabled by default] return __gets_warn (__str); ^ /tmp/cccLhZgy.o: In function `main': user.cpp:(.text.startup+0x87): warning: the `gets' function is dangerous and should not be used. user.cpp:(.text.startup+0x6a): warning: the `gets' function is dangerous and should not be used.