LeetCode [350] Intersection of Two Arrays II

350. Intersection of Two Arrays II

Easy

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?

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class Solution { public: vector<int> intersect(vector<int>& nums1, vector<int>& nums2) { unordered_map<int, int> mp;//number, count for(auto n:nums1) mp[n]++; vector<int> ret; for(auto n:nums2){ if(mp.count(n) && mp[n]>0){ mp[n]--; ret.push_back(n); } } return ret; } };