图的广度优先搜索 （参考算法导论）

#__author__=lx

#__date__=2011-10-03

#__brief__=BFS



from collections import deque



def BFS( G, s ):

        d = []

        color = []

        p = []

        L = deque()



        for i in range( len( G ) ):

                if i != s:

                        color.append( 'white' )

                        d.append( 'helloworld' )

                        p.append( None )

                else:

                        color.append( 'gray' )

                        d.append( 0 )

                        p.append( None )



        L.append( s )



        while ( len( L ) != 0 ):

                u = L.popleft()

                

                for v in G[u]:

                        if cmp( color[v-1],'white' ) == 0:

                                color[v-1] = 'gray'

                                d[v-1] = d[u] + 1

                                p[v-1] = u

                                L.append(v-1)

                color[u] = 'black'

                print u + 1



if __name__ == "__main__":

        l1 = [ 2, 3 ]

        l2 = [ 4, 5, 1 ]

        l3 = [ 6, 7, 1 ]

        l4 = [ 2, 8 ]

        l5 = [ 2, 8 ]

        l6 = [ 3, 7 ]

        l7 = [ 3, 6 ]

        l8 = [ 4, 5 ]



        l = [ l1, l2, l3, l4, l5, l6, l7, l8 ]



        BFS( l, 1 )