244. Shortest Word Distance II

This is a follow up of Shortest Word Distance. The only difference is now you are given the list of words and your method will be called repeatedly many times with different parameters. How would you optimize it?

Design a class which receives a list of words in the constructor, and implements a method that takes two words word1 and word2 and return the shortest distance between these two words in the list.

For example,
Assume that words = ["practice", "makes", "perfect", "coding", "makes"].

Given word1 = “coding”, word2 = “practice”, return 3.
Given word1 = "makes", word2 = "coding", return 1.

Note:
You may assume that word1 does not equal to word2, and word1 and word2 are both in the list.

这道题的答案超时了，待更新。。。

public class WordDistance {
    private String[] strs;
    
    public WordDistance(String[] words) {
        strs = new String[words.length];
        for (int i = 0; i < words.length; i ++) {
            this.strs[i] = words[i];
        }
    }

    public int shortest(String word1, String word2) {
        int p1 = -1, p2 = -1, mindis = Integer.MAX_VALUE;
        for (int j = 0; j < strs.length; j ++) {
            if (strs[j].equals(word1)) {
                p1 = j;
            }
            if (strs[j].equals(word2)) {
                p2 = j;
            }
            if (p1 != -1 && p2 != -1) {
                mindis = Math.min(mindis, Math.abs(p1 - p2));
            }
        }
        return mindis;
    }
}

// Your WordDistance object will be instantiated and called as such:
// WordDistance wordDistance = new WordDistance(words);
// wordDistance.shortest("word1", "word2");
// wordDistance.shortest("anotherWord1", "anotherWord2");

附上新的答案，采用hashmap和list来存储单词和位置，搜索时直接调出单词位置。代码如下：

public class WordDistance {
    HashMap<String,ArrayList<Integer>> map = new HashMap<String,ArrayList<Integer>>();

    public WordDistance(String[] words) {
        for (int i = 0; i < words.length; i++) {
            if(!map.containsKey(words[i])) {
                map.put(words[i], new ArrayList<Integer>());
            }
            map.get(words[i]).add(i);
        }
    }

    public int shortest(String word1, String word2) {
        int shortest = Integer.MAX_VALUE;
        ArrayList<Integer> list1 = map.get(word1);
        ArrayList<Integer> list2 = map.get(word2);
        for (Integer l1:list1) {
            for (Integer l2:list2) {
                shortest = Math.min(shortest, Math.abs(l1 - l2));
            }
        }
        return shortest;
    }
}

// Your WordDistance object will be instantiated and called as such:
// WordDistance wordDistance = new WordDistance(words);
// wordDistance.shortest("word1", "word2");
// wordDistance.shortest("anotherWord1", "anotherWord2");