2248. Intersection of Multiple Arrays

Problem

Given a 2D integer array nums where nums[i] is a non-empty array of distinct positive integers, return **the list of integers that are present in *each array* of** nums** sorted in ascending order**.   *Example 1:*

Input: nums = [[3,1,2,4,5],[1,2,3,4],[3,4,5,6]]
Output: [3,4]
Explanation: 
The only integers present in each of nums[0] = [3,1,2,4,5], nums[1] = [1,2,3,4], and nums[2] = [3,4,5,6] are 3 and 4, so we return [3,4].

Example 2:

Input: nums = [[1,2,3],[4,5,6]]
Output: []
Explanation: 
There does not exist any integer present both in nums[0] and nums[1], so we return an empty list [].

  Constraints:

• 1 <= nums.length <= 1000

• 1 <= sum(nums[i].length) <= 1000

• 1 <= nums[i][j] <= 1000

• All the values of nums[i] are unique.

Solution (Java)

class Solution {
    public List<Integer> intersection(int[][] nums) {
        List<Integer> ans = new ArrayList<>();
        int[] count = new int[1001];
        for (int[] arr : nums) {
            for (int i : arr) {
                ++count[i];
            }
        }
        for (int i = 0; i < count.length; i++) {
            if (count[i] == nums.length) {
                ans.add(i);
            }
        }
        return ans;
    }
}

Explain:

nope.

Complexity:

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