Compilare: user.cpp: In function ‘void PREFIX()’: user.cpp:18:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2 ; i < A.size(); ++ i) ^ user.cpp: In function ‘void KMP()’: user.cpp:33:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1 ; i < B.size() ; ++ i) ^ user.cpp:41:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(Q == A.size() -1) ^ user.cpp: In function ‘int main()’: user.cpp:57:41: 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:58:43: 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) ; ^