350 两个数组的交集 II

https://leetcode.cn/leetbook/read/top-interview-questions-easy/x2y0c2/

https://leetcode.cn/problems/intersection-of-two-arrays-ii/description/

cost: 9m43s

class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        if (nums1.size() > nums2.size()) {
            return this->intersect(nums2, nums1);
        }
        unordered_map<int,int> m;
        for (const int v : nums1) {
            m[v]++;
        }
        vector<int> r = {};
        for (const int v : nums2) {
            if (m.count(v)) {
                m[v]--;
                r.push_back(v);
                if (m[v] == 0) {
                    m.erase(v);
                }
            }
        }
        return r;
    }
};

• 时间复杂度：O(n1+n2)
• 空间复杂度：O(min(n1, n2))