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.

解题思路

首先用map存储数组1里出现的元素，然后检查这些元素是否也在数组2中存在，如果存在则将该元素添加到返回的数组中。

实现代码

// Runtime: 8 ms
public class Solution {
    public int[] intersection(int[] nums1, int[] nums2) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int num : nums1) {
            map.put(num, 1);
        }

        int len = 0;
        for (int num : nums2) {
            if (map.containsKey(num) && map.get(num) == 1) {
                map.put(num, 2);
                ++len;
            }
        }

        int[] nums = new int[len];
        int i = 0;
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            if (entry.getValue() == 2) {
                nums[i++] = entry.getKey();
            }
        }
        return nums;
    }
}