#38 Count and Say

最新推荐文章于 2022-04-17 12:59:49 发布

原创最新推荐文章于 2022-04-17 12:59:49 发布 · 172 阅读

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Description

The count-and-say sequence is the sequence of integers with the first five terms as following:

```
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 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.

Examples

Example 1:

Input: 1
Output: “1”

Example 2:

Input: 4
Output: “1211”

解题思路

看了半天题hmmmmmm

其实是仿照斐波那契数列？

前面的数字和后面的字符串没什么关系……只是index而已

class Solution {
    public String getAnswer(String str){
        int i, j;
        char[] s = str.toCharArray();
        i = 0;
        String answer = "";
        int count = 0;
        while(i < str.length() - 1){
            count = 1;
            while(i < str.length() - 1 && s[i] == s[i + 1]){
                count ++;
                i++;
            }
            answer += String.valueOf(count);
            answer += s[i];
            i++;
        }
        if(i == str.length() - 1)
            answer = answer + "1" + s[i];
        return answer;
    }
    public String countAndSay(int n) {
        String[] answer = new String[30];
        int i;
        answer[0] = "1";
        for(i = 1; i < n; i++){
            answer[i] = getAnswer(answer[i - 1]);
        }
        return answer[n - 1];
    }
}