What is graph? Representation. Need to represent graph in computer. 3 usual types of representation - List of Edges, Connection List, Connection Matrix. Simple enumeration of edges: For this example list of nodes is {1, 2}, {2, 1}, {1, 3}, {3, 1}, {2, 3}, {3, 2}, {2, 5}, {5, 2}, {3, 4}, {4, 3}. Can be used 2 arrays from and to. Can be used array of pairs.