leetcode38

public class Solution {
    public string CountAndSay(int n) {
        //1
            //11
            //21
            //1211
            //111221
            //312211
            //13112221
            //1113213211            

            if (n == 1)
            {
                return "1";
            }
            else
            {
                var list = new List<string>();
                list.Add("1");
                var result = "";
                var pre = "";
                for (int i = 1; i < n; i++)
                {
                    pre = list[i - 1];
                    var c = pre[0];
                    var newrow = new StringBuilder();
                    var count = 1;
                    for (int j = 1; j < pre.Length; j++)
                    {
                        var cur = pre[j];
                        if (c != cur)
                        {
                            newrow.Append(count).Append(c);
                            count = 1;
                            c = cur;
                        }
                        else
                        {
                            count++;
                        }
                    }
                    newrow.Append(count).Append(c);
                    list.Add(newrow.ToString());
                }
                result = list[list.Count - 1];
                return result;
            }
    }
}