38. 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 nth sequence.

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

好多人理解不动题目？unbelievable！

class Solution {public:    string countAndSay(int n) {        string first = "1";        string next;                while(n - 1){//也可以这样写 while( --n)            next = "";// 这句话容易忘            for(int i = 0; i < first.size(); ){                char c = first[i];                int len = 0;                while(i + len < first.size() && first[i + len] == c) len++;                i += len;                next.push_back('0' + len);//也可以这样写 cur += to_string(count) + res[i];                next.push_back(c);            }            first = next;            n--;        }        return first;            }};