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"]

 

class Solution {public:    vector
     
       generateAbbreviations(string word) {        vector
      
       res;        dfs(0,"",res,false,word);        return res;    }private:    void dfs(int idx,string tmp,vector
       
        &res,bool prevNum,string word)    {        if(idx==word.size()){            res.push_back(tmp);            return;        }        dfs(idx+1,tmp+word[idx],res,false,word);        if(!prevNum)        {            for(int len = 1;len+idx<=word.size();len++)            {                dfs(idx+len,tmp+to_string(len),res,true,word);            }        }    }};