***ANSWER IN PYTHON PLEASE***

1. Breadth First Search. Breadth First Search (BFS) is a versatile and efficient strategy for systematically visiting all the nodes in a graph. Given a graph G=(X,E) and a starting point xX, BFS can be described as the following sequence of steps. 1. mark all nodes of G as "unseen". 2. initialize a list seen =[x] and mark x as seen. 3. loop over the elements y in the list seen and, in each step, visit the node y and add all of y 's neighbors that have not been marked as "seen" to the list seen and mark them as seen