Count and Say

佚名 6年前 (2019-04-25) 随笔 1054人围观抢沙发百度已收录

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.

SRE实战互联网时代守护先锋，助力企业售后服务体系运筹帷幄！一键直达领取阿里云限量特价优惠。

Given an integer n, generate the nth sequence.

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

class Solution {
public:
    string countAndSay(int n) 
	{
		if (n <= 0) return "";
		int count = 1;
		string res("1");
		while (count < n)
		{
			string tmp;
			char pre = '0';
			int num = 0;
			for (int i = 0; i < res.size(); i++)
			{
				if (res[i] == pre)
					num++;
				else
				{
					if (pre != '0')
					{
						tmp.push_back(num + '0');
						tmp.push_back(pre);
					}
					pre = res[i];
					num = 1;
				}
			}
			tmp.push_back(num + '0');
			tmp.push_back(pre);
			res = tmp;
			count++;
		}
		return res;
    }
};