ShortestWordDistanceII.java

import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

public class ShortestWordDistanceII {

    private Map<String, List<Integer>> map;

    public ShortestWordDistanceII(String[] words) {
        map = new HashMap<String, List<Integer>>();
        for (int i = 0; i < words.length; i++) {
            List<Integer> list = map.computeIfAbsent(words[i], k -> new LinkedList<>());
            list.add(i);
        }
    }

    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;
    }
}