350. Intersection of Two Arrays II

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

Example: Given nums1 = [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?

Use two pointers

• What if nums1's size is small compared to nums2's size? Which algorithm is better?

Use Hashmap.

• 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?

public class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        int i=0,j=0;
        Arrays.sort(nums1);
        Arrays.sort(nums2);

        int[] res = new int[nums1.length > nums2.length ? nums2.length : nums1.length];
        int k = 0;

        while(i < nums1.length && j < nums2.length){
            if(nums1[i] == nums2[j]){
                res[k++] = nums1[i++];
                j++;
            }else{
               int t = nums1[i] > nums2[j] ? j++ : i++;
            }
        }

        return Arrays.copyOfRange(res, 0, k);
    }
}