LeetCode 350. Intersection of Two Arrays II题目分析代码

public class Solution {
    /**
     * @param nums1 an integer array
     * @param nums2 an integer array
     * @return an integer array
     */
    public int[] intersection(int[] nums1, int[] nums2) {
        // Write your code here
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        for(int i = 0; i < nums1.length; ++i) {
            if (map.containsKey(nums1[i]))
                map.put(nums1[i], map.get(nums1[i]) + 1); 
            else
                map.put(nums1[i], 1);
        }

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

        for (int i = 0; i < nums2.length; ++i)
            if (map.containsKey(nums2[i]) &&
                map.get(nums2[i]) > 0) {
                results.add(nums2[i]);
                map.put(nums2[i], map.get(nums2[i]) - 1); 
            }

        int result[] = new int[results.size()];
        for(int i = 0; i < results.size(); ++i)
            result[i] = results.get(i);

        return result;
    }
}