[Leetcode] Count and Say

weixin_33754913

于 2019-01-08 04:01:02 发布

阅读量65

点赞数

本文介绍了一种特殊的整数序列生成方法，即计数与描述序列。通过递归算法，从初始值1开始，逐步生成序列中的每一项。文章详细解释了序列的生成规则，并提供了C++代码实现。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

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.

递推。

 1 class Solution {
 2 public:
 3     string say(string s) {
 4         string res;
 5         char tag = s[0];
 6         int count = 1;
 7         for (int i = 1; i <= s.length(); ++i) {
 8             if (s[i] == tag) {
 9                 ++count;
10             } else {
11                 res.push_back('0' + count);
12                 res.push_back(tag);
13                 tag = s[i];
14                 count = 1;
15             }
16         }
17         return res;
18     }
19     
20     string countAndSay(int n) {
21         string s;
22         if  (n == 0) return s;
23         s = "1";
24         for (int i = 1; i < n; ++i) {
25             s = say(s);
26         }
27         return s;
28     }
29 };