Graphs

Although a tree is a pretty good way to represent hierarchical data, we can't represent circular or cyclic dependencies in a tree because we always have a single and unique path to go from one node to another. However, there are more complex scenarios that have a cyclic structure inherently. For example, consider a road network. There can be multiple ways to go from one place (places can be represented as nodes) to another. Such a set of scenarios can be better represented using graphs.

Unlike a tree, a graph has to store data for the nodes, as well as for the edges between the nodes. For example, in any road network, for each node (place), we have to store the information about which other nodes (places) it connects to. This way, we can form a graph with all the required nodes and edges. This is called an unweighted graph. We can add weights, or more information, to each of the edges. For our road network example, we can add the distance of each edge (path) from one node (place...