Adjacency list representation

An Adjacency list representation of Graph G = {V, E} contains an array of adjacency lists mentioned by adj of V list. For each of the vertex u?V, adj[u] contains all vertices adjacent to u in the graph G.

Consider the graph of Figure.

Figure: A Graph

Given is the adjacency list representation of graph of above Figure:

adj [1] = {2, 3, 5}

adj [2] = {1, 4}

adj [3] = {1, 4, 5}

adj [4] = {2, 3, 5}

 adj [5] = {1, 3, 4}

An adjacency matrix representation of a Graph G=(V, E) is a matrix

The adjacency matrix for the graph of Figure is following:

Observe that the matrix is symmetric along the main diagonal. If we described the adjacency matrix as A and the transpose as A^T , then for undirected graph G as above, A = A^T.