Given two integer arrays nums1 and nums2, return an array of their intersection. Each element in the result must be unique and you may return the result in any order.
Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [9,4]
Explanation: [4,9] is also accepted.
Constraints:
1 <= nums1.length, nums2.length <= 1000
0 <= nums1[i], nums2[i] <= 1000
Solutions
Solution 1: Hash Table or Array
First, we use a hash table or an array $s$ of length $1001$ to record the elements that appear in the array $nums1$. Then, we iterate through each element in the array $nums2$. If an element $x$ is in $s$, we add $x$ to the answer and remove $x$ from $s$.
After the iteration is finished, we return the answer array.
The time complexity is $O(n+m)$, and the space complexity is $O(n)$. Here, $n$ and $m$ are the lengths of the arrays $nums1$ and $nums2$, respectively.