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
    
      intersect(vector
     
      & nums1, vector
      
       & nums2) {        vector
       
         res;        map
        
          r1;        for(auto num: nums1)            r1[num]++;        for(auto num: nums2)            if(r1[num]>0){                res.push_back(num);                r1[num]--;            }        return res;    }};