Compilare: main.cpp: In function 'void build_pref()': main.cpp:9:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1, m = 0; i < p.size(); ++i) { ~~^~~~~~~~~~ main.cpp: In function 'void kmp()': main.cpp:22:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0, j = 0; j < t.size();) { ~~^~~~~~~~~~ main.cpp:31:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i == p.size()) { ~~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:46:36: 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); ^ main.cpp:47:38: 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); ^