599. Minimum Index Sum of Two Lists

Leetcode Hash Table

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.

分析

考查HashMap的基本操作:map.containsKey(), map.put(), map.get()

public String[] findRestaurant(String[] list1, String[] list2) {
    Map<String, Integer> map = new HashMap<>();
    int i = 0, min = Integer.MAX_VALUE, cur = 0;
    List<String> res = new ArrayList<>();
    for (String str: list1)
        map.put(str, i++);

    i = 0;
    for (String str: list2) {
        if (map.containsKey(str)) {
            cur = i + map.get(str);
            if (cur < min) {
                res.clear();
                res.add(str);
                min = cur;
            } else if (cur == min) {
                res.add(str);
                min = cur;
            }
        }
        i++;
    } // end for
    return res.toArray(new String[0]);
}