349. Intersection of Two Arrays

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

Example: Given nums1 = [1, 2, 2, 1], nums2 = [2, 2], return [2].

Note:

Each element in the result must be unique.

The result can be in any order.

//TODO: you don't really need the set after sort arrays.
public class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        int i=0, j=0;
        Set<Integer> set  = new HashSet<>();
        Arrays.sort(nums1);
        Arrays.sort(nums2);
        while( i < nums1.length && j < nums2.length){
            if(nums1[i] > nums2[j]){
                j++;
            }else if(nums1[i] < nums2[j]){
                i++;
            }else{
                set.add(nums1[i]);
                i++;j++;
            }
        }

        int[] res = new int[set.size()];
        int k =0;
        for(Integer v : set){
            res[k++] = v;
        }

        return res;
    }
}

You can also use set

public class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        Set<Integer> set = new HashSet<>();
        Set<Integer> res = new HashSet<>();

        for(int v : nums1){
            set.add(v);
        }
        for(int v : nums2){
            if(set.contains(v)) res.add(v);    
        }

        int[] r = new int[res.size()];
        int k = 0;
        for(int i : res){
            r[k++] = i;
        }

        return r;
    }
}