The count-and-say sequence 实现

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.

class Solution {
public:
    string countAndSay(int n) {
        string res = "1";
        string cur = "1";
　　　　　
　　     if (1 == n)
　　　　　    return res;        

        for (int i=1; i<n; i++)
        {
            res.clear();            //进行下次计算，情况当前
            int nCurLen = cur.size();
            for (int j=0; j<nCurLen; j++)
            {
                int nCount = 1;
                
                while (cur[j]==cur[j+1] && j+1<nCurLen)
                {
                    ++nCount;       // 计数+1
                    ++j;            // 字符后移
                }
                
                res += nCount+'0';
                res += cur[j];
                nCount =1;
            }
            
            cur = res;
        }
        
        return res;
    }
};