Compilare: user.cpp: In function ‘void prefix()’: user.cpp:13:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i < a.length(); i++) { ^ user.cpp: In function ‘void match()’: user.cpp:26:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; i < b.length(); i++) { ^ user.cpp:33:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == a.length()) { ^ user.cpp: In function ‘int main()’: user.cpp:41:36: 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:42:38: 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); ^