Compilare: user.cpp: In function ‘int main()’: user.cpp:17:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= a.size(); i++) { ^ user.cpp:23:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (r < a.size() && a[r-l] == a[r]) r++; ^ user.cpp:30:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i <= b.size(); i++) { ^ user.cpp:35:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (r-l < a.size() && r < b.size() && a[r-l] == b[r]) r++; ^ user.cpp:35:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (r-l < a.size() && r < b.size() && a[r-l] == b[r]) r++; ^ user.cpp:36:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (r-l == a.size()) { ^ user.cpp:8:36: 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:9:38: 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); ^