Generalized Abbreviation

Source

• leetcode: 320

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"]

java

public class Solution {
    public List<String> generateAbbreviations(String word) {
        List<String> res = new ArrayList<String>();
        int len = word.length();
        res.add(len==0 ? "" : String.valueOf(len));
        for(int i = 0 ; i < len ; i++)
            for(String right : generateAbbreviations(word.substring(i+1))){
                String leftNum = i > 0 ? String.valueOf(i) : "";
                res.add( leftNum + word.substring(i,i + 1) + right );
            }
        return res;
    }
}