Array Intersection

# Array Intersection ## Difficulty Easy ## Tags `array`, `hash table`, `sorting` ## Problem Statement Given two integer arrays `nums1` and `nums2`, return an array of their intersection. Each element in the result must appear as many times as it shows in **both** arrays. You may return the result in any order. ## Constraints - 1 ≤ nums1.length, nums2.length ≤ 1000 - 0 ≤ nums1[i], nums2[i] ≤ 1000 ## Signatures ### Python ```python def intersect(nums1: List[int], nums2: List[int]) -> List[int]: pass ``` ### Java ```java public class Solution { public List<Integer> intersect(List<Integer> nums1, List<Integer> nums2) { return null; } } ``` ### Csharp ```csharp public class Solution { public IList<int> intersect(IList<int> nums1, IList<int> nums2) { throw new NotImplementedException(); } } ``` ### Cpp ```cpp class Solution { public: vector<int> intersect(vector<int> nums1, vector<int> nums2) { } }; ``` ### C ```c int* intersect(int* nums1, int* nums2) { } ``` ### Ruby ```ruby def intersect(nums1, nums2) end ``` ### Perl ```perl sub intersect { my ($self, @args) = @_; } ``` ### Scala ```scala object Solution { def intersect(nums1: List[Int], nums2: List[Int]): List[Int] = { } } ``` ### Haskell ```haskell intersect :: ... -> ... intersect args = undefined ``` ### Clojure ```clojure (defn intersect [nums1 nums2] ) ``` ### Scheme ```scheme (define (intersect nums1 nums2) ) ``` ## Examples ### Example 1 **Input:** ``` nums1 = [1, 2, 2, 1] nums2 = [2, 2] ``` **Output:** ``` [2, 2] ``` **Explanation:** 2 appears twice in both arrays. ### Example 2 **Input:** ``` nums1 = [4, 9, 5] nums2 = [9, 4, 9, 8, 4] ``` **Output:** ``` [4, 9] or [9, 4] ``` **Explanation:** 4 and 9 each appear at least once in both. ### Example 3 **Input:** ``` nums1 = [1, 2, 3] nums2 = [4, 5, 6] ``` **Output:** ``` [] ``` **Explanation:** No common elements. ## Hints 1. **Hash Map approach**: Count occurrences in nums1, then iterate through nums2. If element exists with count > 0, add to result and decrement count. 2. **Sorting approach**: Sort both arrays, use two pointers to find common elements. 3. If one array is much smaller, iterate through the smaller one.