Shortest Word Distance II

Source

• leetcode: 244

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.

Java

public class WordDistance {
    private Map<String, List<Integer>> map;

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

    public int shortest(String word1, String word2) {
        List<Integer> list1 = map.get(word1);
        List<Integer> list2 = map.get(word2);
        int ret = Integer.MAX_VALUE;
        for(int i = 0, j = 0; i < list1.size() && j < list2.size(); ) {
            int index1 = list1.get(i), index2 = list2.get(j);
            if(index1 < index2) {
                ret = Math.min(ret, index2 - index1);
                i++;
            } else {
                ret = Math.min(ret, index1 - index2);
                j++;
            }
        }
        return ret;
    }
}