[算法导论]BFS @ Python

class Graph:

    def __init__(self):

        self.V = []

class Vertex:

    def __init__(self, x):

        self.key = x

        self.color = 'white'

        self.d = 10000

        self.pi = None

        self.adj = []

class Solution:

    def BFS(self, G, s):

        for u in G.V:

            if u != s:

                u.color = 'white'

                u.d = 10000

                u.pi = None

        s.color = 'gray'

        s.d = 0

        s.pi = None

        Q = []

        Q.append(s)

        while Q != []:

            u = Q.pop(0)

            for v in u.adj:

                if v.color == 'white':

                    v.color = 'gray'

                    v.d = u.d + 1

                    v.pi = u

                    Q.append(v)

            u.color = 'black'

if __name__ == '__main__':

    G = Graph()

    r = Vertex('r')

    s = Vertex('s')

    t = Vertex('t')

    u = Vertex('u')

    v = Vertex('v')

    w = Vertex('w')

    x = Vertex('x')

    y = Vertex('y')

    r.adj = [s, v]

    s.adj = [r, w]

    t.adj = [u, w, x]

    u.adj = [t, x, y]

    v.adj = [r]

    w.adj = [s, t, x]

    x.adj = [t, u, w, y]

    y.adj = [u, x]

    G.V = [r, s, t, u, v, w, x, y]

    m = Solution()

    m.BFS(G, s)

    for v in G.V:

        if v != s:

            print v.key, v.color, v.d, v.pi.key