PROBLEM：
Given two arrays, write a function to compute their intersection.
Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].
Note:
- Each element in the result must be unique.
- The result can be in any order.
SOLVE：
class Solution {
public:
vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
unordered_set<int> set1(nums1.begin(),nums1.end());
vector<int> res;
for(auto a:nums2)
if(set1.erase(a)==1) //erase方法如果删除会返回1，否则返回0
res.push_back(a);
return res;
}
};