350. Intersection of Two Arrays II

Problem:

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.

A possible solution:

class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        unordered_map<int,int> m;
        vector<int> res;
        for(auto a: nums1) m[a]++;
        for(auto a: nums2)
        {
            if(m[a]-- >0) res.push_back(a);
        }
        return res;
    }
};