320. 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"]

 

 

 

public IList<string> GenerateAbbreviations(string word) {
        List<string> res = new List<string>();
        BackTracking(word,0,"",res,0);
        return res;
    }
    
    private void BackTracking(string word,int sentinel, string cur, List<string> res, int isNumberbefore)
    {
        if(sentinel == word.Length)
        {
            if(isNumberbefore ==0) res.Add(cur);
            else res.Add(cur+isNumberbefore);
        }
        else
        {
            if(isNumberbefore > 0) BackTracking(word, sentinel+1,cur+isNumberbefore+word[sentinel],res,0);
            else BackTracking(word, sentinel+1,cur+word[sentinel],res,0);
            BackTracking(word, sentinel+1,cur,res,isNumberbefore+1);
        }
    }