349. Intersection of Two Arrays

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

Example:
Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].

Note:

Each element in the result must be unique.
The result can be in any order.

求两个集合的交集结果元素必须唯一

C++（6ms）：

 1 class Solution {
 2 public:
 3     vector<int> intersection(vector<int>& nums1, vector<int>& nums2) {
 4         unordered_set<int> s(nums1.begin(),nums1.end()) ;
 5         vector<int> ans ;
 6         for (int i = 0; i < nums2.size();i++ ){
 7            if(s.count(nums2[i])){
 8               ans.push_back(nums2[i]) ;
 9               s.erase(nums2[i]);
10            }
11         }
12         return ans;
13     }
14 };

java(5ms):

 1 class Solution {
 2     public int[] intersection(int[] nums1, int[] nums2) {
 3         Set<Integer> set = new HashSet<>() ;
 4         for(int i = 0 ; i < nums1.length ; i++){
 5             set.add(nums1[i]) ;
 6         }
 7         List<Integer> list = new ArrayList<>() ;        
 8         for(int i : nums2){
 9             if (set.contains(i)){
10                 list.add(i) ;
11                 set.remove(i) ;
12             }
13         }
14         int[] res = new int[list.size()] ;
15         for(int i = 0  ; i < list.size() ; i++){
16             res[i] = list.get(i) ;
17         }
18         return res ;
19     }
20 }