I'd love to hear some opinions on my solution.

def noPrefix(words): word_dict = dict()

for i, word in enumerate(words):
    if word in word_dict:
        word_dict[word].append(i)
    else:
        word_dict[word] = [i]

bad_ind = float('inf')
for i, word in enumerate(words):
    if i == bad_ind:
        break

    # Check substrings
    for j in range(len(word)-1):
        if word[0:j+1] in word_dict:
            bad_ind = min( bad_ind, max(i, word_dict[word[0:j+1]][0]) )

    # Check if full string repeats
    if len(word_dict[word]) > 1:
        bad_ind = min(bad_ind, word_dict[word][1])

if bad_ind == float('inf'):
    print("GOOD SET")
else:
    print("BAD SET")
    print(words[bad_ind])

return