A Common-Sense Guide to Data Structures and Algorithms

While the Facebook and Twitter examples are similar, the nature of the relationships in each example are different. Because relationships in Twitter are one-directional, we use arrows in our visual implementation, and such a graph is known as a directed graph. In Facebook, where the relationships are mutual and we use simple lines, the graph is called a non-directed graph. While a simple hash table can be used to represent a graph, a more robust object-oriented implementation can be used as well.