Compilare: user.cpp: In function ‘int calc(int, int, int, bool)’: user.cpp:19:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(cate > k) ^ user.cpp:21:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(len == n) return cate == k; ^ user.cpp:21:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(len == n) return cate == k; ^ user.cpp: In function ‘int main()’: user.cpp:59:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1;i<=n;++i)s[i]-='0'; ^ user.cpp:50:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("frumusete.in","r",stdin); ^ user.cpp:51:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("frumusete.out","w",stdout); ^ user.cpp:53:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%u\n", &t); ^ user.cpp:56:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%u\n", &k); ^ user.cpp:57:19: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (s + 1); ^ /tmp/ccAlMt7I.o: In function `main': user.cpp:(.text.startup+0x9a): warning: the `gets' function is dangerous and should not be used.