Leetcode 38 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.

這個題目的意思就是此時的字串由上一個字串來定義，也就是count+say，程式碼如下：

class Solution {
    public String countAndSay(int n) {
        StringBuffer cur = new StringBuffer("1");
        StringBuffer prev;
        int count = 0;
        char say;
        for(int i = 1 ; i < n ; i++){
            prev = cur;
            cur = new StringBuffer();
            count = 1;
            say = prev.charAt(0);
            for(int j = 1,len = prev.length() ; j < len;j++){
                if(prev.charAt(j) != say){
                    cur.append(count).append(say);
                    count = 1;
                    say = prev.charAt(j);
                }else{
                    count++;
                }
            }
            cur.append(count).append(say);
        }
        return cur.toString();
    }
}