如何找到列表列表中的公共元素？ [英] How to find common elements in list of lists?

问题描述

我想弄清楚如何比较n个列表来找到共同的元素。
例如：

I'm trying to figure out how to compare an n number of lists to find the common elements. For example:

p=[ [1,2,3],
    [1,9,9],
      ..
      ..
    [1,2,4]

>> print common(p)
>> [1]

现在如果我知道元素的数量，我可以做比较：

Now if I know the number of elements I can do comparions like:

for a in b:
  for c in d:
    for x in y:
...

但是如果我不知道有多少元素p，它不工作。我看过这个比较两个列表的解决方案
http://stackoverflow.com/a/1388864/1320800< a>

but that wont work if I don't know how many elements p has. I've looked at this solution that compares two lists http://stackoverflow.com/a/1388864/1320800

但是花了4个小时试图找到一个递归的方法，一个解决方案仍然逃避我，所以任何帮助将高度赞赏！

but after spending 4 hrs trying to figure a way to make that recursive, a solution still eludes me so any help would be highly appreciated!

推荐答案

您正在查找所有子列表的集合交集，并且您应该用于集合操作的数据类型是一组：

You are looking for the set intersection of all the sublists, and the data type you should use for set operations is a set:

result = set(p[0])
for s in p[1:]:
    result.intersection_update(s)
print result

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