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 nth sequence.

原题：点击打开链接

class Solution {public:    string countAndSay(int n){        string s = "1";        while(--n > 0){            string tmp;            tmp.clear();                        int size = s.length(), cnt = 1;            char lastChar = s[0];                        for(int i=1;i<size;i++){                if(lastChar == s[i]){                   cnt++;                        }else{                   tmp += cnt + '0';                   tmp += lastChar;                   lastChar = s[i];                   cnt = 1;                }            }                        tmp += cnt + '0';            tmp += lastChar;            s = tmp;        }        return s;    }};