LeetCode-Generalized Abbreviation

Write a function to generate the generalized abbreviations of a word.

Example:

Given word = "word", return the following list (order does not matter):

["word", "1ord", "w1rd", "wo1d", "wor1", "2rd", "w2d", "wo2", "1o1d", "1or1", "w1r1", "1o2", "2r1", "3d", "w3", "4"]

Solution:

public class Solution {
    public List<String> generateAbbreviations(String word) {
        List<String> res = new ArrayList<String>();
        StringBuilder builder = new StringBuilder();

        getAbbrRecur(builder,0,word,res);

        return res;
    }

    public void getAbbrRecur(StringBuilder builder, int cur, String word, List<String> res){
        if (cur >= word.length()){            
            // We get an abbr.
            res.add(builder.toString());
            return;
        }
        
        // Use this to reset the builder for backtracking. Together with setLength()
        int len = builder.length();
        
        // deal with not change word[cur].
        builder.append(word.charAt(cur));
        getAbbrRecur(builder,cur+1,word,res);
        builder.setLength(len);

        int maxLen = word.length()-cur;
        for (int i=1;i<=maxLen;i++){
            // Change the following i chars into abbr number. 
            builder.append(i);
            // Add the next char into buffer, as it should not be changed.
            if (cur+i < word.length()) builder.append(word.charAt(cur+i));
            getAbbrRecur(builder,cur+i+1,word,res);
            builder.setLength(len);
        }
    }
}