Compilare: user.cpp: In function ‘int find_hash(int)’: user.cpp:37:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a[hash].size(); ++i) ^ user.cpp: In function ‘int main(int, const char**)’: user.cpp:70:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < b.size() - 1; ++i) ^ user.cpp:72:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = i + 1; j < b.size(); ++j) ^ user.cpp:51:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prog.in", "r", stdin); ^ user.cpp:52:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prog.out", "w", stdout); ^ user.cpp:54:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &t); ^ user.cpp:60:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:63:28: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^