leetcode——Intersection of Two Arrays II

题目：

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

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

class Solution {public:    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {        vector<int> res;        unordered_map<int, int> m;        for (auto i : nums1)         {            m[i]++;        }                for (auto i : nums2)         {            //if(m[i]-- > 0) res.push_back(i);//如果用这个空间复杂度就是m+n了            auto it = m.find(i);            if (it != m.end() && it->second-- > 0)//空间复杂度是n            {                res.push_back(i);            }        }                return res;    }};

如果nums1和nums2是以排序数组，有没有更好的方案？

class Solution {public:    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {        //sort(nums1.begin(), nums1.end());        //sort(nums2.begin(), nums2.end());        int n1 = (int)nums1.size(), n2 = (int)nums2.size();        int i1 = 0, i2 = 0;        vector<int> res;        while(i1 < n1 && i2 < n2){            if(nums1[i1] == nums2[i2]) {                res.push_back(nums1[i1]);                i1++;                i2++;            }            else if(nums1[i1] > nums2[i2]){                i2++;            }            else{                i1++;            }        }        return res;    }};