LeetCode Minimum Index Sum of Two Lists

Posted 2020-10-06 Dylan_Java_NYC

原题链接在这里：https://leetcode.com/problems/minimum-index-sum-of-two-lists/description/

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<String> res = new ArrayList<String>();
 4         int minIndexSum = Integer.MAX_VALUE;
 5         HashMap<String, Integer> hm = new HashMap<String, Integer>();
 6         for(int i = 0; i<list1.length; i++){
 7             hm.put(list1[i], i);
 8         }
 9         
10         for(int j = 0; j<list2.length; j++){
11             if(hm.containsKey(list2[j])){
12                 int i = hm.get(list2[j]);
13                 if(i+j < minIndexSum){
14                     res.clear();
15                     res.add(list2[j]);
16                     minIndexSum = i+j;
17                 }else if(i+j == minIndexSum){
18                     res.add(list2[j]);
19                 }
20             } 
21         }
22         
23         return res.toArray(new String[res.size()]);
24     }
25 }