Compilare: user.cpp: In function ‘void preKmp(std::string)’: user.cpp:17:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<x.length()) ^ user.cpp: In function ‘void KMP(std::string)’: user.cpp:35:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(j<s.length()) ^ user.cpp:40:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i>=k.length()) ^ user.cpp: In function ‘int main()’: user.cpp:58:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<match.size();++i) ^ user.cpp:51:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("strmatch.in","r",stdin); ^ user.cpp:52:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("strmatch.out","w",stdout); ^