SRM419 div1 250

undo.cpp

 string getText(vector<string> commands, vector<int> time) {
        string ret = "";
        for(int i=commands.size()-1; i>=0;){
            istringstream iss(commands[i]);
            vector<string> tokens {istream_iterator<string>{iss}, istream_iterator<string>{}};
            if(tokens[0]=="undo"){
                int ustep = stoi(tokens[1]);
                int cur_time = time[i];
                i-=1;
                while(i>=0 && cur_time - time[i] <= ustep){
                    i-=1; //ignore both undo and type
                }
            }
            else{//"type"
                ret.insert(0, tokens[1]);
                --i;
            }
        }
        return ret;
    }

 //petr
 public string getText(string[] commands, int[] time) { 
        string[] stateBefore = new string[commands.Length + 1]; 
        stateBefore[0] = ""; 
        for (int i = 0; i < commands.Length; ++i) 
        { 
            string[] p = commands[i].Split(' '); 
            if (p[0] == "type") 
            { 
                stateBefore[i + 1] = stateBefore[i] + p[1]; 
            } 
            else 
            { 
                int j = i; 
                int len = int.Parse(p[1]); 
                while (j > 0 && time[j - 1] + len >= time[i]) 
                    --j; 
                stateBefore[i + 1] = stateBefore[j]; 
            } 
        } 
        return stateBefore[commands.Length]; 
  }