350. Intersection of Two Arrays II

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Problem

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

Example 1:

Input: nums1 = [1,2,2,1], nums2 = [2,2]
Output: [2,2]

Example 2:

Input: nums1 = [4,9,5], nums2 = [9,4,9,8,4]
Output: [4,9]

Code

class Solution {
    public int[] intersect(int[] nums1, int[] nums2) {
        HashMap<Integer, Integer> map = new HashMap<>();
        for(int num : nums1) {
            map.put(num, map.getOrDefault(num, 0) + 1);
        }

        List<Integer> res = new ArrayList<>();

        for(int num : nums2) {
            if(map.containsKey(num) && map.get(num) != 0) {
                res.add(num);
                map.put(num, map.get(num) - 1);
            }
        }

        int[] arr = new int[res.size()];
        for(int i = 0; i < arr.length; i++) {
            arr[i] = res.get(i);
        }

        return arr;
    }
}