Compilare: user.cpp: In function ‘int main()’: user.cpp:11:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<strlen(s)) ^ user.cpp:6:10: warning: unused variable ‘j’ [-Wunused-variable] int i,k,j=0; ^ user.cpp:7:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("compress.in","r",stdin); ^ user.cpp:8:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("compress.out","w",stdout); ^ user.cpp:9:9: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ /tmp/ccVeKUJz.o: In function `main': user.cpp:(.text.startup+0x6c): warning: the `gets' function is dangerous and should not be used.