LeetCode | Count and Say

题目：

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.

思路：

题目理解比较费时，就是一个常规的递归问题。

代码：

class Solution {
public:
    string countAndSay(int n) {
        if(n==1)
        {
            return "1";
        }
        else if(n==2)
        {
            return "11";
        }
        else
        {
            string str = countAndSay(n-1);
            string result;
            int pre;
            int cur=str[0]-'0';
            int count=1;
            for(int i=1;i<str.size();i++)
            {
                pre=cur;
                cur=str[i]-'0';
                if(pre==cur)
                {
                    count++;
                }
                else
                {
                    result.push_back(count+'0');
                    result.push_back(pre+'0');
                    count=1;
                }
            }
            result.push_back(count+'0');
            result.push_back(cur+'0');
            return result;
        }
    }
};