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.

题目解析：

其实题目很简单，就是计算个数，并填充到新的数组中。由于对C++不熟悉，如何给string加上一个字符还不太懂，不过参考了别人的总算写出来了，但其中机理还是不明白。string类型，除了可以直接加字符串或者string变量外，还能加上一个字符！

class Solution {
public:
    string countAndSay(int n) {
        string str;
        str = "1";
        while(--n){
            string temp;
            char pre = str[0];
            int count = 1;
            for(string::size_type i = 1;i < str.size();i++){
                if(str[i] == pre)
                    count++;
                else{
                    char ch = count + '0';
                    temp = temp + ch + pre;
                    pre = str[i];
                    count = 1;
                }
            }
            char ch = count + '0';
            temp = temp + ch + pre;
            str = temp;
        }
        return str;
    }
};