words = ['giraffe', 'elephant', 'ant', 'tiger', 'racoon', 'cat', 'hedgehog', 'mouse']

['hedgehog', 'giraffe', 'elephant', 'tiger', 'racoon']

words = ['giraffe', 'elephant', 'ant', 'tiger', 'racoon', 'cat', 'hedgehog', 'mouse']
def get_results(_start, _current, _seen):
 if all(c in _seen for c in words if c[0] == _start[-1]):
  yield _current
 else:
   for i in words:
    if i[0] == _start[-1]:
     yield from get_results(i, _current+[i], _seen+[i])

new_d = [list(get_results(i, [i], []))[0] for i in words]
final_d = max([i for i in new_d if len(i) == len(set(i))], key=len)

import networkx as nx
import matplotlib.pyplot as plt
words = ['giraffe', 'elephant', 'ant', 'tiger', 'racoon', 'cat',
     'hedgehog', 'mouse']
G = nx.DiGraph()
G.add_nodes_from(words)
for word1 in words:
  for word2 in words:
    if word1 != word2 and word1[-1] == word2[0]:
      G.add_edge(word1, word2)
nx.draw_networkx(G)
plt.show()
print(nx.algorithms.dag.dag_longest_path(G))