he count-and-say sequence is the sequence of integers beginning as follows:

​​1, 11, 21, 1211, 111221, ...​​​​1​​ is read off as ​​"one 1"​​ or ​​11​​.

​​11​​ is read off as ​​"two 1s"​​ or ​​21​​.

​​21​​ is read off as ​​"one 2​​, then ​​one 1"​​ or ​​1211​​.

n, generate the nth

Note: The sequence of integers will be represented as a string.

直接模拟

class Solution {
public:
  string countAndSay(int n) {
    string str;
    for (int i = 1; i <= n; i++){
      if (i == 1){
        str = "1";
      }
      else{
        string tmp;
        int len = str.size();
        int j = 0;
        int ini = 0;
        while (j <= len){
          if (j<len&&str[j] == str[ini]){
            j++;
          }
          else{
            tmp.append(to_string(j-ini));
            tmp += str[ini];//如果用to_string返回的是ASCII码
            ini = j;
            j++;
          }
        }
        str = tmp;
      }
    }
    return str;
  }
};