349. Intersection of Two Arrays

Problem

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.

  Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2]

Example 2:

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

Solution

class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        boolean[] occ = new boolean[1001];
        for (int k : nums1) {
            occ[k] = true;
        }
        List<Integer> res = new ArrayList<>();
        for (int j : nums2) {
            if (occ[j]) {
                occ[j] = false;
                res.add(j);
            }
        }
        int[] result = new int[res.size()];
        for (int i = 0; i < res.size(); i++) {
            result[i] = res.get(i);
        }
        return result;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).