#!/usr/bin/python
# vim:fileencoding=utf-8

class Vertex(object):
    def __init__(self, depth, parent, CWR):
        self.depth = depth
        self.parent = parent
        self.CWR = CWR
        self.children = []


def create_vocabulary():
    with open('./words.txt', 'r') as f:
        vocabulary = f.read().split()
    return vocabulary


def solve_CWR(vertex, vocabulary):
    depth = vertex.depth
    if depth == 3:
        return
    elif depth == 0:
        is_valid_extension = lambda cwr, word: cwr[0][2] == word[0]
    elif depth == 1:
        is_valid_extension = lambda cwr, word: cwr[1][2] == word[2]
    elif depth == 2:
        is_valid_extension = (lambda cwr, word: cwr[0][0] == word[0] and
                                                cwr[2][0] == word[2])
    for word in vocabulary:
        if is_valid_extension(vertex.CWR, word):
            CWR = vertex.CWR[:]
            CWR.append(word)
            newchild = Vertex(depth+1, vertex, CWR)
            vertex.children.append(newchild)
            solve_CWR(newchild, vocabulary)


def print_solutions(vertex):
    if vertex.depth == 3:
        print vertex.CWR
        return
    for child in vertex.children:
        print_solutions(child)


if __name__ == '__main__':
    import random

    vocabulary = create_vocabulary()
    CWR = [vocabulary[random.randint(0, len(vocabulary)-1)]]
    root = Vertex(0, None, CWR)
    solve_CWR(root, vocabulary)
    print_solutions(root)