Longest String Chain

class Solution {
public:
    
    bool check(string s, string s1)
    {
        if(s1.length()-s.length()!=1)
            return false;
        int cnt=0;
        int j=0,i=0;
       while(j<s.length()&&i<s1.length()&&s[j]==s1[i])
        {
            
                j++,i++;
            
        }
        if(j==s.length())
        {
            return true;
        }
        
        return (s.substr(j,s.length()-j).compare(s1.substr(i+1,s1.length()-i-1))==0);
       
        
        
    }
    bool static comparator(string a,string b)
    {
        return a.length()<b.length();
    }
    int longestStrChain(vector<string>& w) {
         
        int maxi=0;
        sort(w.begin(),w.end(),comparator);
        vector<int>dp(w.size(),1);
        for(int i=1;i<w.size();i++)
        {
            for(int j=0;j<i;j++)
            {
                if(check(w[j],w[i])&&dp[i]<dp[j]+1)
                {
                  
                    dp[i]=dp[j]+1;
                    if(dp[i]>dp[maxi])
                    maxi=i;
                }
                
            }
        }
        
        return dp[maxi];
    }
};