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 [].

<解題>

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

Time: O(N*M) Space: O(1)