Compilare: user.cpp: In function ‘void dung_canh()’: user.cpp:30:19: warning: suggest parentheses around comparison in operand of ‘|’ [-Wparentheses] if(x>n||y>n||x<1|y<1) continue; ^ user.cpp: In function ‘void dfs(int)’: user.cpp:57:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<adj[u].size();i++) ^ user.cpp: In function ‘int main()’: user.cpp:115:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("matrice2.in","r",stdin); ^ user.cpp:116:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("matrice2.out","w",stdout); ^ user.cpp:118:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&q); ^ user.cpp:123:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&a[(i-1)*n+j]); ^ user.cpp:133:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d%d",&x,&y,&u,&v); ^