[LeetCode350] 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].

Note:

• Each element in the result should appear as many times as it shows in both arrays.
• The result can be in any order.

分类：Hash Table  Two Pointers  Sort

代码：

class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        vector<int> res;
        map<int,int> hash;
        
        for(auto num : nums1)
            ++hash[num];
            
        for(auto num : nums2)
        {
            auto it = hash.find(num);
            if(it != hash.end())//找到了 数量减1
            {
                 if(it->second >= 1)
                {
                    res.push_back(num);
                    --hash[num];
                }
            }
        }
        
        return res;
    }
};