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38. Count and Say

时间:2018-10-18 13:17:15      阅读:152      评论:0      收藏:0      [点我收藏+]

标签:pac   rate   har   output   and   space   example   length   wing   

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"
//Time: O(n * m), Space: O(1)    
public String countAndSay(int n) {
        if (n == 1) {
            return "1";
        }
        
        String pre = "1";
        
        for (int i = 2; i <= n; i++) {
            int count = 1;
            StringBuilder sb = new StringBuilder();
            
            for (int j = 1; j <= pre.length(); j++) {
                if (j == pre.length() || pre.charAt(j) != pre.charAt(j - 1)) {
                    sb.append(count);
                    sb.append(pre.charAt(j - 1));
                    count = 1;
                } else {
                    count++;
                }
            }
            
            pre = sb.toString();
        }
        
        return pre;
    }

 

38. Count and Say

标签:pac   rate   har   output   and   space   example   length   wing   

原文地址:https://www.cnblogs.com/jessie2009/p/9809782.html

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