Topological sorting using Kahn's algorithm

Let's assume that we have some tasks to do, and each of the tasks has some dependencies that mean that the dependent tasks should be done first before doing the actual task. The problem arises when we have an interrelationship between tasks and dependencies. Now, we need to come up with a proper order for completing the tasks. We need a special type of sorting so that we can sort these connected tasks without violating our rules for finishing the tasks. Topological sorting will be the right choice for solving such problems. In topological sorting, a directed edge AB from vertex A to B is sorted in such a way that A will always come before B in the ordering. This will be applicable for all the vertices and edges. Another important factor for applying a topological sort is that the graph must be a DAG. Any DAG has at least...