350. Intersection of Two Arrays II

https://leetcode.com/problems/intersection-of-two-arrays-ii/discuss/82450/Java-O(m+n)-using-Hash-and-List

 

 

class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        if(nums1 == null || nums2 == null) return null;
        HashMap<Integer, Integer> map1 = new HashMap<>();
        HashMap<Integer, Integer> map2 = new HashMap<>();
        for(int i = 0; i < nums1.length; i++) {
            map1.put(nums1[i], map1.getOrDefault(nums1[i], 0)+1);
        }
        for(int i = 0; i < nums2.length; i++) {
            map2.put(nums2[i], map2.getOrDefault(nums2[i], 0)+1);
        }
        Set<Integer> set1 = map1.keySet();
        Set<Integer> set2 = map2.keySet();
        List<Integer> list1 = new ArrayList<>(set1);
        List<Integer> res = new ArrayList<>();
        for(int i = 0; i < list1.size(); i++) {
            if(set2.contains(list1.get(i))) {
                for(int j = 0; j < Math.min(map1.get(list1.get(i)), map2.get(list1.get(i))); j++) {
                    res.add(list1.get(i));
                }
            }
        }
        int[] res1 = new int[res.size()];
        for(int i = 0; i < res.size(); i++) {
            res1[i] = res.get(i);
        }
        return res1;
               
    }
}