LeetCode.599 Minimum Index Sum of Two Lists （经典：哈希表对字符串去重和List与数组间的转换）

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本文介绍了一种算法，用于帮助两个人从各自的餐厅列表中找到共同喜欢且列表索引之和最小的餐厅。通过使用哈希映射记录第一个列表中的餐厅及其索引，再遍历第二个列表来查找匹配项，从而实现高效查找。

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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:

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：

class Solution {
    public String[] findRestaurant(String[] list1, String[] list2) {
        //给定两个菜单的字符串数组，找出其中相同的菜单下标和最小的下标的菜单名，如果存在下标和相同，则全部输出
        //注意：菜单项最多1000，每个菜单的名字最多30个字符，下标从0开始计算。每个菜单中不存在重复的菜单名。
        //思路：先求出相同项，然后下标和相同的存入相同的List数组中
        List<String> list=new ArrayList<>();;
        
        //参考队列
        HashMap<String,Integer> hm=new HashMap<String,Integer>();
        
        for(int i=0;i<list1.length;i++){
            hm.put(list1[i],i);
        }
        int min=Integer.MAX_VALUE;
        for(int i=0;i<list2.length;i++){
            Integer j=hm.get(list2[i]);
            if(j!=null&&i+j<=min){
                //清楚list中的数据
                if(i+j<min){
                    //存在更小的，清空之前的
                    list.clear();
                    min=i+j;
                }
                //添加元素，相同下标和
                list.add(list2[i]);
            }
            
        }
        
        //输出结果
        return list.toArray(new String[list.size()]);
    }
}