350. Intersection of Two Arrays II（LeetCode）

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.

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         sort(nums1.begin(), nums1.end());
   5         sort(nums2.begin(), nums2.end());
   6         int len1 = nums1.size();
   7         int len2 = nums2.size();
   8
   9         int i = 0;
  10         int j = 0;
  11         vector<int> vet;
  12         while (i < len1&&j < len2)
  13         {
  14             if (nums1[i] == nums2[j])
  15             {
  16                 vet.push_back(nums1[i]);
  17                 i++;
  18                 j++;
  19
  20             }
  21             else
  22             {
  23                 if (nums1[i] < nums2[j])
  24                 {
  25                     i++;
  26                 }
  27                 else
  28                 {
  29                     j++;
  30                 }
  31             }
  32         }
  33         return vet;
  34     }
  35 };