[LeetCode]Count and Say

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 n^th sequence.

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

一开始没看懂题目，找了一下别人的翻译。。。

第一个序列是 1， 第二个序列由第一个生成， 叫 一个1 ，写为 11

问 第n个是什么 

迭代

class Solution {
public:
    string revolution(string s)
	{
		string ret;
		char pre =s[0];
		int count = 1;
		for(int i = 1; i < s.size(); i ++)
		{
			if(s[i]==pre)
			{
				count ++;
			}else{
				
				char tmp =  count+'0';
				ret = ret + tmp + pre;
				pre = s[i];
				count = 1;
			}
		}
		char tmp =  count+'0';
		ret = ret + tmp + pre;
		return   ret;
	}
    string countAndSay(int n) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
		string ret = "1";
		int j = 1;
		while( j< n){
			ret=revolution(ret);
			j++;
		}
		return ret;
    }
};