Compilare: user.cpp: In function ‘void buildZ()’: user.cpp:25:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < t.length(); ++i) ^ user.cpp:34:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (i+z[i] < t.length() && t[z[i]] == t[i+z[i]]) ^ user.cpp: In function ‘int main()’: user.cpp:62:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < ans.size(); ++i) ^ user.cpp:54:34: 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:55:36: 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); ^