Graphs can be stored in adjacency tables,
The adjacency list is n linked lists,
Linked list can be simulated with array (faster than vector).
const int N;
void add(int a,int b)
(nodes in different linked lists can have the same value, indicating the node number. Use ne [IDX] to find the next adjacent point of the current point and H [E [IDX]] to find the adjacent point of the adjacent contact)