#Leetcode# 350. Intersection of Two Arrays II

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

 

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

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]

Note:

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

Follow up:

• What if the given array is already sorted? How would you optimize your algorithm?
• What if nums1's size is small compared to nums2's size? Which algorithm is better?
• What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

代码：

class Solution {
public:
    vector<int> intersect(vector<int>& nums1, vector<int>& nums2) {
        vector<int> ans;
        int n = nums1.size(), m = nums2.size();
        map<int, int> mp;
        for(int i = 0; i < n; i ++) mp[nums1[i]] ++;
        for(int i = 0; i < m; i ++) {
            if(mp[nums2[i]]-- > 0)
                ans.push_back(nums2[i]);
        }
        return ans;
    }
};

　　刚开始理解错了。。。脑子不清醒哟