350. Intersection of Two Arrays II

原题链接：https://leetcode.com/problems/intersection-of-two-arrays-ii/description/
实现如下：

import java.util.*;

/**
 * Created by clearbug on 2018/2/26.
 */
public class Solution {

    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(Arrays.toString(s.intersect(new int[]{1, 2, 2, 1}, new int[]{2, 2})));
    }

    public int[] intersect(int[] nums1, int[] nums2) {
        if (nums1 == null || nums2 == null) {
            return new int[0];
        }
        Map<Integer, Integer> map = new HashMap<>(nums1.length);
        for (int i = 0; i < nums1.length; i++) {
            map.put(nums1[i], map.getOrDefault(nums1[i], 0) + 1);
        }
        ArrayList<Integer> list = new ArrayList<>(nums2.length);
        for (int i = 0; i < nums2.length; i++) {
            if (map.containsKey(nums2[i]) && map.get(nums2[i]) > 0) {
                list.add(nums2[i]);
                map.put(nums2[i], map.get(nums2[i]) - 1);
            }
        }
        int[] res = new int[list.size()];
        int i = 0;
        for (int item : list) {
            res[i++] = item;
        }
        return res;
    }

}