Added Topological Sort description

Author: vldmrkl

README.md

@@ -112,6 +112,10 @@ __Properties__
 
 ###### View the algorithm in [action][shell-toptal]
 
+### Topological
+
+From [Wikipedia][topological-wiki]: In the field of computer science, a topological sort or topological ordering of a directed graph is a linear ordering of its vertices such that for every directed edge uv from vertex u to vertex v, u comes before v in the ordering. For instance, the vertices of the graph may represent tasks to be performed, and the edges may represent constraints that one task must be performed before another; in this application, a topological ordering is just a valid sequence for the tasks. A topological ordering is possible if and only if the graph has no directed cycles, that is, if it is a directed acyclic graph (DAG). Any DAG has at least one topological ordering, and algorithms are known for constructing a topological ordering of any DAG in linear time.
+
 ### Time-Complexity Graphs
 
 Comparing the complexity of sorting algorithms (Bubble Sort, Insertion Sort, Selection Sort)
@@ -206,6 +210,8 @@ Mathematically a bijective function is used on the characters' positions to encr
 [shell-wiki]: https://en.wikipedia.org/wiki/Shellsort
 [shell-image]: https://upload.wikimedia.org/wikipedia/commons/d/d8/Sorting_shellsort_anim.gif "Shell Sort"
 
+[topological-wiki]: https://en.wikipedia.org/wiki/Topological_sorting
+
 [linear-wiki]: https://en.wikipedia.org/wiki/Linear_search
 [linear-image]: http://www.tutorialspoint.com/data_structures_algorithms/images/linear_search.gif