Given two arrays, write a function to compute their intersection.

Example:
Givennums1=[1, 2, 2, 1],nums2=[2, 2], return[2, 2].

Note:

• Each element in the result should appear as many times as it shows in both arrays.
• The result can be in any order.

Follow up:

• What if the given array is already sorted? How would you optimize your algorithm?
• What if nums1 's size is small compared to nums2 's size? Which algorithm is better?
• What if elements of nums2 are stored on disk, and the memory is limited such that you cannot load all elements into the memory at once?

class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        if (nums1 == null || nums2 == null) return new int[0];

        List<Integer> list = new ArrayList<>();
        Arrays.sort(nums1);
        Arrays.sort(nums2);
        int index1 = 0, index2 = 0;

        while (index1 < nums1.length && index2 < nums2.length){
            if (nums1[index1] == nums2[index2]){
                list.add(nums1[index1]);
                index1++;
                index2++;
            }
            else if (nums1[index1] < nums2[index2]){
                index1++;
            }
            else{
                index2++;
            }
        }

        int[] ans = new int[list.size()];
        for (int i = 0; i < list.size(); i++){
            ans[i] = list.get(i);
        }

        return ans;
    }
}