每日一题: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 nth sequence.

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

解答

public class Solution {
    public String countAndSay(int n) {
        if(n == 1){
            return "1";
        }
        String str = countAndSay(n - 1)+ "%";
        StringBuffer sb = new StringBuffer();
        int count = 1;
        for(int i = 0; i < str.length() - 1; i++){
            if(str.charAt(i) == str.charAt(i + 1)){
                count++;
            }else{
                sb.append(String.valueOf(count));
                sb.append(str.charAt(i));
                count = 1;
            }
        }
        return sb.toString();
    }
}

注解

采用递归的方式解决，然后处理过程就不多说啦。