擅长:python、mysql、java
<p>也许这样的事情对你有用(这是O(n))</p>
<pre><code>from collections import defaultdict
students = fillStudentList()
sameLastNames = defaultdict(list)
for student in students:
sameLastNames[student.lastName].append(student)
sameLastNames = {k:v for k,v in sameLastNames.iteritems() if len(v)>1}
</code></pre>