LeetCode 349. 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.

Code1：

class Solution {public:    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {        vector<int> intersection;        map<int,int> m;        sort(nums1.begin(),nums1.end());        sort(nums2.begin(),nums2.end());        nums1.erase(unique(nums1.begin(),nums1.end()),nums1.end());        nums2.erase(unique(nums2.begin(),nums2.end()),nums2.end());        for(int i=0;i<nums1.size();i++) m[nums1[i]]++;        for(int i=0;i<nums2.size();i++) m[nums2[i]]++;        for(auto & n:m){            if(n.second==2) intersection.push_back(n.first);        }        return intersection;            }};

Code2：

class Solution {public:    vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {        unordered_set<int> m(nums1.begin(), nums1.end());        vector<int> res;        for (auto a : nums2)            if (m.count(a)) {                res.push_back(a);                m.erase(a);            }        return res;    }};