Compilare: user.cpp: In function ‘long long int get(std::string&)’: user.cpp:14:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int l = 1; l < A.size(); l++) { ^ user.cpp:18:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < A.size(); i++) { ^ user.cpp: In function ‘std::string merge(std::string, std::string)’: user.cpp:65:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i++) { ^ user.cpp:67:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (l <= b.size() && a.substr(i, l) == b.substr(0, l)) { ^ user.cpp: In function ‘long long int attempt2(std::string)’: user.cpp:77:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < A.size(); i++) { ^ user.cpp: In function ‘bool checkPrefix(std::string, std::string)’: user.cpp:112:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (idx < A.size()) { ^ user.cpp:118:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (modelIdx == model.size()) { ^ user.cpp: In function ‘long long int attempt3(std::string)’: user.cpp:130:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < A.size() - 1; i++) { ^ user.cpp:132:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i; j < A.size() - 1; j++) { ^ user.cpp: In function ‘int main()’: user.cpp:147:54: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infinitepatternmatching.in", "r", stdin); ^ user.cpp:148:56: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infinitepatternmatching.out", "w", stdout); ^