【LeetCode】38. Count and Say

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Difficulty:easy

 More:【目录】LeetCode Java实现

Description

https://leetcode.com/problems/count-and-say/

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.

Example 1:

Input: 1
Output: "1"

Example 2:

Input: 4
Output: "1211"

Intuition

Straightforward

Solution

    public String countAndSay(int n) {
        String str="1";
        if(n==1)
            return str;
        while(n>1){
            str=getNext(str);
            n--;
        }
        return str;
    }
    
    private String getNext(String str){
        StringBuilder sb = new StringBuilder();
        int i=0;
        while(i<str.length()){
            char num=str.charAt(i);
            int count=0;
            while(i<str.length() && str.charAt(i)==num){
                i++;
                count++;
            }
            sb.append(count).append(num);
        }
        return sb.toString();
    }

Complexity

What I‘ve learned

 More:【目录】LeetCode Java实现

【LeetCode】38. Count and Say

标签：ref   sequence   leetcode   https   inpu   builder   tostring   rms   int   

原文地址：https://www.cnblogs.com/yongh/p/11665845.html