Share my AC DP solution


  • 1
    T
    public class Solution {
        public string Encode(string s) {
            return Helper(s,0,s.Length-1,new string[s.Length,s.Length]);
        }
        
        private string Helper(string s, int low,int high, string[,] dp){
            
            if(low > high)
                return "";
            
            if(low == high){
                dp[low,high] = s[low]+"";
                return dp[low,high];
            }
            
            if(dp[low,high] != null){
                return dp[low,high];
            }
            
            string subStr = s.Substring(low,high-low+1);
            string result = subStr;
            
            for(int i = low;i<high;i++){
                string r = Helper(s,low,i,dp)+Helper(s,i+1,high,dp);
                if(r.Length < result.Length)
                    result = r;
                    
                //Console.WriteLine(low+","+high+":"+result);
            }
            
            dp[low,high] = result;
            
            for(int i = 0;i<subStr.Length;i++){
                string repeatStr = subStr.Substring(0,i+1);
                if(repeatStr != null && subStr.Replace(repeatStr,"").Length == 0){
                    
                    string ss = subStr.Length/repeatStr.Length+"["+dp[low,low+i]+"]";
                    
                    if(ss.Length < result.Length)
                        result = ss;
                }
            }
            
            dp[low,high] = result;
            
            return dp[low,high];
        }
        
    }
    

  • 0
    I

    In your second loop, isnt the complexity of substr.Replace() O(n)? So then doesnt that make it so that solving each subproblem is n^2 in the worst case cause you go through all the prefixes for each substring and check to see if it s a repeating pattern?


  • 0
    T

    Yes, But I don't have any idea how to solve this problem. prefix is not enough.


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