Graph theory plus edge algorithm

Many graph theory algorithms have a function

struct Edge {    int to;    int W;    int next;} Edge[n * 2];int Cnt_edge = 0;void add_edge (int from, int. to, Int. W) {    edge[cnt_edge].to = to;    EDGE[CNT_EDGE].W = W;    Edge[cnt_edge].next = Head[from];    Head[from] = cnt_edge++;} Memset (Head,-1, sizeof head);

I've been wrestling with the meaning of this function for a long time ...

In fact, a diagram is stored with an adjacency table.

Cnt_edge is to give each side a label, starting from 0.

The edge[i].to represents the point at which the edge of the section I is pointing, and Edge[i].next represents the ordinal of the next edge of the I-bar.

Head[from] Indicates the ordinal of an edge that is the initial node from the first point.

Example (casually painted = =#):

Presence Edge 1,3 1,4 2,5 2,6 4,3 5, 36 edges

After calling the function Add_edge in turn, you can get

edge[0].to=3; Edge[0].next=-1; head[1]=0;

edge[1].to=4; edge[1].next=0; Head[1]=1;

edge[2].to=5; Edge[2].next=-1; head[2]=2;

edge[3].to=6; edge[3].next=5; head[2]=3;

edge[4].to=3; Edge[4].next=-1; head[4]=4;

edge[5].to=3; Edge[5].next=-1; head[5]=5;

A graph means:

Meow. How do you draw the direction of the arrows?

Graph theory plus edge algorithm