# leetcode\_349

## 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]
```

## Note:

* Each element in the result must be unique.
* The result can be in any order.

## Solutions

1. **hashset**

```cpp
class Solution {
public:
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
        unordered_set<int> s(nums1.begin(), nums1.end());

        vector<int> res;
        for (auto & num : nums2)
            if (s.erase(num))
                res.push_back(num);

        return res;
    }
};
```