【LeetCode】38. Count and Say

最新推荐文章于 2023-06-09 10:21:32 发布

weixin_33969116

最新推荐文章于 2023-06-09 10:21:32 发布

阅读量59

点赞数

本文介绍了一种特殊的整数序列——计数与说数序列，并提供了一个C++实现方案来生成序列中的第n项。该序列从1开始，后续每一项都是对前一项的描述。例如1被描述为“one1”即11；11被描述为“two1s”即21等。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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.

思路：对于下一个字符串= 对于当前字符串：∑(字符个数+字符)

例如1211，下一个字符串就是count(1)+'1'+count(2)+'2'+count(1)+'1'=111221

class Solution {
public:
    string countAndSay(int n) {
        string ret = "1";
        if(n == 1)
            return ret;
        n --;
        while(n --)
        {
            string next;
            char last = ret[0];
            int i = 1;
            int count = 1;
            while(i < ret.size())
            {
                
                while(i < ret.size() && ret[i] == last)
                {
                    i ++;
                    count ++;
                }
                if(i < ret.size() && ret[i] != last)
                {
                    next += to_string(count);
                    next += last;
                    
                    count = 1;
                    last = ret[i];
                    i ++;
                }
            }
            //i == ret.size()
            next += to_string(count);
            next += last;
            ret = next;
        }
        return ret;
    }
};