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?
1 // class Solution { 2 // public: 3 // vector<int> intersect(vector<int>& nums1, vector<int>& nums2) { 4 // unordered_map<int, int> ctr; 5 // vector<int> res; 6 // for (auto i : nums1) ctr[i]++; 7 // for (auto i : nums2) { 8 // if (ctr.count(i) > 0 && ctr[i] > 0) { 9 // ctr[i]--; 10 // res.push_back(i); 11 // } 12 // } 13 // return res; 14 // } 15 // }; 16 17 class Solution { 18 public: 19 vector<int> intersect(vector<int>& nums1, vector<int>& nums2) { 20 vector<int> res; 21 22 sort(nums1.begin(), nums1.end()); 23 sort(nums2.begin(), nums2.end()); 24 25 int i1 = 0, i2 = 0; 26 while(i1<nums1.size() && i2<nums2.size()){ 27 if(nums1[i1] == nums2[i2]){ 28 res.push_back(nums1[i1]); 29 i1++; 30 i2++; 31 } 32 else if(nums1[i1] < nums2[i2]){ 33 i1++; 34 } 35 else{ 36 i2++; 37 } 38 } 39 40 return res; 41 } 42 };