599. Minimum Index Sum of Two Lists

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

Solution：Hashset + 依次pass

思路：

Time Complexity: O(m+n) Space Complexity: O(N)

Solution Code：

public String[] findRestaurant(String[] list1, String[] list2) {
    Map<String, Integer> map = new HashMap<>();
    List<String> res = new LinkedList<>();
    int minSum = Integer.MAX_VALUE;
    for (int i=0;i<list1.length;i++) map.put(list1[i], i);
    for (int i=0;i<list2.length;i++) {
        Integer j = map.get(list2[i]);
        if (j != null && i + j <= minSum) {
            if (i + j < minSum) { res.clear(); minSum = i+j; }
            res.add(list2[i]);
        }
    }
    return res.toArray(new String[res.size()]);
}