# 350.Intersection of Two Arrays II

350.Intersection of Two Arrays II

Given two arrays, write a function to compute their intersection.
Example 1:
Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]
Example 2:
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]
Note:
Each element in the result should appear as many times as it shows in both arrays.
The result can be in any order.
What if the given array is already sorted? How would you optimize your algorithm?
What if nums1's size is small compared to nums2's size? Which algorithm is better?
What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

template <class InputIterator1, class InputIterator2, class OutputIterator>
OutputIterator set_intersection(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,
OutputIterator result);
template <class InputIterator1, class InputIterator2, class OutputIterator, class Compare>
OutputIterator set_intersection(InputIterator1 first1, InputIterator1 last1,
InputIterator2 first2, InputIterator2 last2,

class Solution {
public:
vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
vector<int> res;
if(nums1.empty() || nums2.empty()) return res;
unordered_map<int ,int>common;
for(auto n: nums1)
common[n]++;
for(auto n: nums2)
{
if(common.count(n) && common[n])
{
common[n]--;
res.push_back(n);
}
}
return res;
}
};