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public class Solution {
    class Word implements Comparable<Word> {
        String wd;
        int idx;
        Word(String word, int idx) {
            this.wd = word; this.idx = idx;
        }
        public int compareTo(Word w) {
            if (this.wd.length() == w.wd.length())
                return this.wd.compareTo(w.wd);
            return w.wd.length() - this.wd.length();
        }
    }
    public List<String> wordsAbbreviation(List<String> dict) {
        int n = dict.size();
        Word[] words = new Word[n+1];
        for(int i =0; i < n; i++) {
            String word = dict.get(i);
            words[i] = new Word(word.charAt(word.length()-1) + word, i);
        }
        words[n] = new Word("", n);
        
        Arrays.sort(words);
        
        int pref = 0;
        for(int i = 0; i < n; i++) {
            String w1 = words[i].wd, w2 = words[i+1].wd;
            int cur = 0;
            if (w1.length() == w2.length()) {
                cur = commonPref(w1, w2);
            }
            String abbr = getAbbr(w1, Math.max(cur, pref));
            pref = cur;
            dict.set(words[i].idx, abbr.length() < w1.length()-1 ? abbr: w1.substring(1));
        }
            
        return dict;
    }
    
    private String getAbbr(String str, int pref) {
        if (pref == 0) {
            pref = 1;
        }
        int count = str.length() - pref - 2;
        return str.substring(1, pref+1) + count + str.charAt(0);
    }
    
    private int commonPref(String s1, String s2) {
        int pref = 0;
        while(pref < s1.length()) {
            if (s1.charAt(pref) != s2.charAt(pref))
                return pref;
            pref++;
        }
        return pref;
    }
}

/*
Make abbreviation for each word.
Then, check each word, if there are some strings which have same abbreviation with it, increase the prefix.
*/
public class Solution {
    public List<String> wordsAbbreviation(List<String> dict) {
        int len=dict.size();
        String[] ans=new String[len];
        int[] prefix=new int[len];
        for (int i=0;i<len;i++) {
            prefix[i]=1;
            ans[i]=makeAbbr(dict.get(i), 1); // make abbreviation for each string
        }
        for (int i=0;i<len;i++) {
            while (true) {
                HashSet<Integer> set=new HashSet<>();
                for (int j=i+1;j<len;j++) {
                    if (ans[j].equals(ans[i])) set.add(j); // check all strings with the same abbreviation
                }
                if (set.isEmpty()) break;
                set.add(i);
                for (int k: set) 
                    ans[k]=makeAbbr(dict.get(k), ++prefix[k]); // increase the prefix
            }
        }
        return Arrays.asList(ans);
    }

    private String makeAbbr(String s, int k) {
        if (k>=s.length()-2) return s;
        StringBuilder builder=new StringBuilder(); 
        builder.append(s.substring(0, k));
        builder.append(s.length()-1-k);
        builder.append(s.charAt(s.length()-1));
        return builder.toString();
    }
}