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# Copyright 2016 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
from collections import defaultdict
def _single_trie(string_to_value_pairs, index):
"""Build a single trie from a dict of input string to output values.
This function assumes that all of the strings in
string_to_value_pairs have the same length.
The input
{'abcd': 'ABCD', 'adef': 'ADEF', 'adeg': 'ADEG'}
creates a trie like this:
{
'a' : {
'b': {'cd' : "ABCD"},
'd' : {
'e' : {
'f' : {'': "ADEF"},
'g' : {'': "ADEG"},
},
},
},
}
"""
dicts_by_indexed_letter = defaultdict(list)
for string, value in string_to_value_pairs:
dicts_by_indexed_letter[string[index]].append((string, value))
output = {}
for char, d in dicts_by_indexed_letter.items():
if len(d) == 1:
string = d[0][0]
value = d[0][1]
output[char] = {string[index + 1:]: value}
else:
output[char] = _single_trie(d, index + 1)
return output
def trie_list_by_str_length(str_to_return_value_dict):
"""Make a list of tries from a dict of input string to output value.
All strings should be all lower case.
"""
dicts_by_length = defaultdict(list)
for string, value in str_to_return_value_dict.items():
dicts_by_length[len(string)].append((string, value))
output = []
for length, pairs in sorted(dicts_by_length.items()):
output.append((length, _single_trie(sorted(pairs), 0)))
return output
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