擅长:python、mysql、java
<p>我不认为写这篇文章是一种理解。考虑来自<a href="https://docs.python.org/3.7/library/collections.html" rel="nofollow noreferrer">^{<cd2>}</a>模块的<a href="https://docs.python.org/3.7/library/collections.html#collections.defaultdict" rel="nofollow noreferrer">^{<cd1>}</a>。在</p>
<pre><code>>>> from collections import defaultdict
>>>
>>> result = defaultdict(list)
>>> for k, v in rating.items():
...: result[v].append(k)
...:
>>> result
>>>
defaultdict(list,
{'excellent': ['bob', 'baxter', 'belle'],
'no pass': ['ben'],
'passing': ['barnum', 'bernice', 'bill', 'bernie'],
'satisfactory': ['beatrice']})
</code></pre>
<p>这有时间复杂性O(n),任何我尝试过的理解,比如</p>
^{pr2}$
<p>在O(n**2)时更糟。在</p>