Leetcode 38 Count and Say

最新推荐文章于 2021-01-13 21:28:45 发布

原创最新推荐文章于 2021-01-13 21:28:45 发布 · 285 阅读

0 ·

CC 4.0 BY-SA版权

本文介绍了一种特殊的数列生成算法——计数与说数序列，通过解析序列生成规则，提供了一个Java实现示例，用于生成指定位置的序列项。

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 with the first five terms as following:

1.     1
2.     11
3.     21
4.     1211
5.     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 where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.

Note: Each term of the sequence of integers will be represented as a string.

这个题目的意思就是此时的字符串由上一个字符串来定义，也就是count+say，代码如下：

class Solution {
    public String countAndSay(int n) {
        StringBuffer cur = new StringBuffer("1");
        StringBuffer prev;
        int count = 0;
        char say;
        for(int i = 1 ; i < n ; i++){
            prev = cur;
            cur = new StringBuffer();
            count = 1;
            say = prev.charAt(0);
            for(int j = 1,len = prev.length() ; j < len;j++){
                if(prev.charAt(j) != say){
                    cur.append(count).append(say);
                    count = 1;
                    say = prev.charAt(j);
                }else{
                    count++;
                }
            }
            cur.append(count).append(say);
        }
        return cur.toString();
    }
}