Problem

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

Example

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]

Code

static int var =[](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        sort(nums1.begin(),nums1.end());
        sort(nums2.begin(),nums2.end());
        int i=0,j=0;
        vector<int> res;
        while(i<nums1.size() && j<nums2.size()){
            if(nums1[i]==nums2[j]){
                res.push_back(nums1[i]);
                i++;
                j++;
            }
            else if(nums1[i]<nums2[j])
                i++;
            else
                j++;
        }
        return res;
    }
};

Result

350. Intersection of Two Arrays II.png