[Leetcode]Intersection of Two Arrays

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

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

Note:

• Each element in the result must be unique.
• The result can be in any order.

class Solution {
public:
    /*algorithm
        1)add nums1 to hash set S
        2)for each number in nums2, check whether it exist in S,if it is add it to result
        time O(m+n)
    */
    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
            unordered_set<int>hash1,hash2;
            vector<int>result;
            for(int i = 0;i < nums1.size();i++){
                hash1.insert(nums1[i]);
            }
            for(int j = 0;j < nums2.size();j++){
                if(hash1.count(nums2[j])){
                    hash2.insert(nums2[j]);
                }
            }
            
            for(auto it = hash2.begin();it != hash2.end();it++){
                result.push_back(*it);
            }
            return result;
    }
};