Compilare: user.cpp: In function ‘void build_prefix(std::string)’: user.cpp:44:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 1; i < a.length(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:65:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < b.length()) ^ user.cpp:69:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < b.length() && b[i] != '*') ^ user.cpp:77:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(b[i] == '*' && i < b.length() ) ^ user.cpp:81:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < words.size(); j++) ^ user.cpp:99:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == words[j].size() - 1) ^ user.cpp:116:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < words.size(); j++) ^