LeetCode38. Count and Say

最新推荐文章于 2025-08-17 23:28:34 发布

原创最新推荐文章于 2025-08-17 23:28:34 发布 · 318 阅读

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#leetcode #String

本文介绍了一种生成计数读数序列的方法，通过递归读取当前字符串并形成新的字符串来生成序列的第n项。该方法适用于整数序列转换为特定形式的字符串表示。

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题目

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, generate the nth term of the count-and-say sequence.

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

思路

写一个递归就是咯、读取当前的String，即形成新的String。

代码

public class Solution {

	//子函数，读取当前的String形成新的String
    public String countAndSay_Sub (String s){
		String result = "";
		int count = 1;
		int i = 0;
		while(i < s.length()){
			while((i + count) < s.length() && s.charAt(i) == s.charAt(i + count))	++ count;
			result = result + count + s.charAt(i);
			i = i + count;
			count = 1;
		}
		return result;
	}
    public String countAndSay(int n) {
        String result = "1";
        for(int i = 1 ; i < n ; ++ i){
            result = countAndSay_Sub(result);
        }
        return result;
    }
}