Compilare: user.cpp: In function ‘int main()’: user.cpp:37:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (j=found=0;j<H[line].size();++j) ^ user.cpp:21:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix2.in","r",stdin); ^ user.cpp:22:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prefix2.out","w",stdout); ^ user.cpp:24:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%s",(S+1)); ^