599. Minimum Index Sum of Two Lists(easy)

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.

/*
暴力的话O（n^2）,可以利用hashtable,用空间来换时间。
*/
class Solution {
public:
    vector<string> findRestaurant(vector<string>& list1, vector<string>& list2) {
        vector<string> res;
        map<string, int> data;
        int minval = INT_MAX;
        for (int i = 0; i < list1.size(); i++){   // 存入hashtable中
            data.insert(pair<string, int>(list1[i], i));
        }
        for (int i = 0; i < list2.size(); i++){
            if (data.find(list2[i]) != data.end()){
               if (data[list2[i]] + i < minval){
                   minval = data[list2[i]] + i;
                   res.clear();
                   res.push_back(list2[i]);
               }else if (data[list2[i]] + i == minval){
                   res.push_back(list2[i]);
               }
            }
        }
        return res;
    }
};