599. Minimum Index Sum of Two Lists

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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:

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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:

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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.

解法1：

用一个hashtable记录每一个restaurant出现的位置，当出现之前出现过的string的时候更新答案。
C++

1

Java

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public class Solution {
    public String[] findRestaurant(String[] list1, String[] list2) {
        List<String> res = new ArrayList<String>();
        if (list1 == null || list2 == null || list1.length == 0 || list2.length == 0) {
            return new String[0];
        }
        Map<String, Integer> map = new HashMap<String, Integer>();
        for (int i = 0; i < list1.length; i++) {
            map.put(list1[i], i);
        }
        int min = Integer.MAX_VALUE;
        for (int i = 0; i < list2.length; i++) {
            if (map.containsKey(list2[i])) {
                int index = map.get(list2[i]);
                if (index + i == min) {
                    res.add(list2[i]);
                } else if (index + i < min) {
                    res.clear();
                    res.add(list2[i]);
                    min = index + i;
                }
            }
        }
        String[] array = new String[res.size()];
        for (int i = 0; i < res.size(); i++) {
            array[i] = res.get(i);
        }
        return array;
    }
}