Compilare: user.cpp: In function ‘void dfs(int, int, int, int)’: user.cpp:21:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < g[left][c].size(); ++i) ^ user.cpp:22:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < g[right][c].size(); ++j) ^ user.cpp: In function ‘int main()’: user.cpp:35:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arbpal.in","r",stdin); ^ user.cpp:36:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arbpal.out","w",stdout); ^ user.cpp:38:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:40:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", a + i, b + i); ^ user.cpp:42:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("\n"); ^ user.cpp:43:14: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(sir); ^ /tmp/ccfCl9Qz.o: In function `main': user.cpp:(.text.startup+0xc3): warning: the `gets' function is dangerous and should not be used.