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.

开始没弄太明白，在找规律，而且以为只能是 1和 2 的组合，终于找到规律了，但却误解了题意，比如连续 4 个 1 会说 4 个 1 而不会说 “2 个 1 ，2 个1”，汗

class Solution {
public:
    string countAndSay(int n) {
    string re("");
	if(n <= 0) return re;
	re += ‘1‘;
	string tmp;
	for (int i = 2; i <= n; ++i)
	{
		tmp = re;
		re.clear();
		for (int j = 0; j < tmp.length();++j)
		{
		    int cnt = 1;
			while(j + 1 < tmp.length() && tmp[j] == tmp[j + 1])
			{
			    ++j;
			    ++cnt;
			}
			re += (cnt + ‘0‘);
			re += tmp[j];
		}
	}
	return re;
    }
};

Count and Say