LeetCode - Count and Say

题目：

The count-and-say sequence is the sequence of integers beginning as follows:
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, generate the n^th sequence.

Note: The sequence of integers will be represented as a string.

思路：

对这些数字进行统计。

package string;

public class CountAndSay {

    public String countAndSay(int n) {
        String s = "1";
        while (--n > 0) {
            StringBuilder sb = new StringBuilder();
            int len = s.length();
            int count = 1;
            for (int i = 1; i <= len; ++i) {
                if (i < len && s.charAt(i) == s.charAt(i - 1)) {
                    ++count;                    
                } else {
                    sb.append((char)(count + '0'));
                    sb.append(s.charAt(i - 1));
                    count = 1;
                }
            }
            
            s = sb.toString();
        }
        
        return s;
    }
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        CountAndSay c = new CountAndSay();
        System.out.println(c.countAndSay(6));
    }

}