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

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2, 2].

Note:

• Each element in the result should appear as many times as it shows in both arrays.
• The result can be in any order.

Follow up:

• 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?

class Solution {public:    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {        map<int, int> map;        vector<int> ret;        for (auto &e : nums1)            ++map[e];        for (auto &e : nums2)        {            if (map.find(e) != map.end() && map[e] !=0)            {                ret.push_back(e);                --map[e];            }        }        return ret;    }};

LeetCode 350. Intersection of Two Arrays II