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two。 Characteristics of adjacency table (undirected graph):

Sometimes the adjacency matrix is not a good choice:

Such as the above figure: the number of edges is relatively small, this structure is undoubtedly a great waste of storage space.

Adjacency table: arrays and linked lists are combined to store.

1.) vertices are stored in an one-digit array.

2.) all the adjacent points of each vertex Vi form a linear table. Because the number of adjacent points is uncertain, we choose a single linked list to store.

two。 Characteristics of adjacency tables (digraphs):

Take the vertices as the adjacency table established at the end of the arc, so that you can easily get the degree of each vertex.

Sometimes in order to determine the entry degree of a vertex or an arc with a vertex as the arc head, we can establish an inverse adjacency table of a directed graph:

3. The characteristics of the adjacency table (network):

For a network graph with weights, you can add another data field to the edge table node definition to store the weights:

Typedef char Vtype / / Vertex type typedef int Etype / / weight type # definde MAXV 100 alternate typedef struct edgeNode / / Edge table node {int adjvex; / / adjacent points store the corresponding subscript Etype weight;// edge weights struct edgeNode * next;} EdgeNode;typedef struct Vnode / / vertex table node {Vtype data; EdgeNode* firstEdge;} VNODE; / / typedef struct {VNODE adjlist [MAXV] Int numV;// current number of vertices int numE;// current number of sides} GraphAdjList; void CreateALGraph (GraphAdjList* G) {int iLecture jLING; EdgeNode* e = NULL; cout > G-> numE; for (iS0 + +) / / create vertex information {cin > > G-> adjlist [I] .data / / enter vertex information G-> adjlist [I] .firstEdge = NULL; / / the edge table node is empty} for (kappa next = j; e-> next = G-> adjlist [I] .firstEdge; / / similar to node- > next = list- > head; list- > head = node; G-> adjlisti] .firstEdge = e in the stack E = new EdgeNode; e-> adjvex = I; e-> next = G-> adjlist [j] .firstEdge; G-> adjlist [j] .firstEdge = e;}}

For an undirected graph, an edge corresponds to two vertices, so I and j are inserted in a loop for n vertices and e edges.

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