Compilare: main.cpp: In function 'void dfs(int)': main.cpp:23:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[start_node].size();i++) ~^~~~~~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:42:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("darp.in", "r", stdin); ^ main.cpp:43:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("darp.out", "w", stdout); ^ main.cpp:46:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ main.cpp:50:30: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^ main.cpp: In function 'void cle()': main.cpp:17:19: warning: iteration 100004 invokes undefined behavior [-Waggressive-loop-optimizations] visited[i]=false; ~~~~~~~~~~^~~~~~ main.cpp:16:18: note: within this loop for(int i=1;i<=nmax;i++) ~^~~~~~