[LeetCode] Count and Say

Problem Statement (link):

The 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.
Given an integer n, generate the nth sequence.
Note: The sequence of integers will be represented as a string.

Analysis:
No particular algorithms applied to this problem. Simply go through n rounds, wherein we calculate the time of each repeated characters and append to output string.

Code:

class Solution {
public:
    string countAndSay(int n) {
        string sout;
        string s="1";
        while(n-->1) {
            sout=helper(s);
            s=sout;
        }
        return s;
    }

    string helper(string s) {
        int count=0;
        char last=s[0];
        string sout="";
        for (int i=0; i<=s.length(); i++) {
            if (s[i]==last) count++;
            else {
                sout+=to_string(count)+s[i-1];
                last=s[i];
                count=1;
            }
        }
        return sout;
    }
};