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# Intersection of Two Arrays

Given two arrays, write a function to compute their intersection.

**Example 1:**

```
Input: 
nums1 = 
[1,2,2,1]
, nums2 = 
[2,2]
Output: 
[2]
```

**Example 2:**

```
Input: 
nums1 = 
[4,9,5]
, nums2 = 
[9,4,9,8,4]
Output: 
[9,4]
```

分析

还是用dictionary counter做，2个for

```
import collections


class Solution:
    def intersection(self, nums1, nums2):
        """
        :type nums1: List[int]
        :type nums2: List[int]
        :rtype: List[int]
        """
        if not nums1 or not nums2:
            return []
        ret =set()
        map = collections.defaultdict(int)
        for i in nums1:
            map[i]+=1
        for i in nums2:
            if map[i]>0:
                ret.add(i)
        return list(ret)
```