# Graph theory

#studying big problems using adjacency list/ matrix

G = {
    'Boston' : [ 'Providence', 'New York' ],
    'Providence' : [ 'Boston', 'New York' ],
    'New York' : [ 'Chicago' ],
    'Chicago ' : [ 'Denver ' , 'Phoenix ' ] ,
    'Denver' : [ 'Phoenix', 'New York' ],
    'Phoenix' : [],
    'Los Angeles' : [ 'Boston' ] }

#working with dictionary :
'''
    G[key] = [value]
    G[key].append(value)

'''
def toolsTest():
    from graph_tools import digraph_example1
    G = digraph_example1()
    print(listNodes(G)) # prints all the nodes
    print('---------------------------------')
    print(listEdges(G)) # prints  the node, destination pairs
    digraphPlot(G)
    deadends=digraphDeadends(G)
    print ( deadends )

    return

def listNodes(G):
    nodes = list(G.keys())
    return nodes

def listEdges(G):
    # edges are the pairs or (nodes, destination)
    edges = []
    for node in G.keys():
        for dest in G[node]:
            edges.append([node,dest])
    return edges

def digraphPlot(G):
    from graphviz import Digraph
    nodes = listNodes(G)
    edges = listEdges(G)
    dot = Digraph( format = 'png')
    for n in nodes:
        dot.node(n)
    for e in edges:
        dot.edge(e[0],e[1])
    dot.render('digraph.dot',view=True)
    return

def digraphDeadends(G):
    deadends = []
    for n in G.keys():
        if (not G[n] ) :
            deadends.append(n)
    return deadends

toolsTest()