原题链接在这里：

题目：

Suppose Andy and Doris want to choose a restaurant for dinner, and they both have a list of favorite restaurants represented by strings.

You need to help them find out their common interest with the least list index sum. If there is a choice tie between answers, output all of them with no order requirement. You could assume there always exists an answer.

Example 1:

Input:["Shogun", "Tapioca Express", "Burger King", "KFC"]["Piatti", "The Grill at Torrey Pines", "Hungry Hunter Steakhouse", "Shogun"]Output: ["Shogun"]Explanation: The only restaurant they both like is "Shogun".

Example 2:

Input:["Shogun", "Tapioca Express", "Burger King", "KFC"]["KFC", "Shogun", "Burger King"]Output: ["Shogun"]Explanation: The restaurant they both like and have the least index sum is "Shogun" with index sum 1 (0+1).

Note:

1. The length of both lists will be in the range of [1, 1000].
2. The length of strings in both lists will be in the range of [1, 30].
3. The index is starting from 0 to the list length minus 1.
4. No duplicates in both lists.

题解：

把list1的element 和对应的index放进HashMap<String, Integer> hm中. 再iterate list2, 如果list2的element在hm中比较index相加是否比minIndexSum小，若比minIndexSum小，清空res重新加, 更新minIndexSum. 若相等直接加进res中.

Time Complexity: O(list1.length + list2.length)

Space: O(list1.length).

AC Java:

1 class Solution { 2     public String[] findRestaurant(String[] list1, String[] list2) { 3         List
     
       res = new ArrayList
      
       (); 4         int minIndexSum = Integer.MAX_VALUE; 5         HashMap
       
         hm = new HashMap
        
         (); 6         for(int i = 0; i