Leetcode记录-Q38-外观数列

解题思路

典型的递归调用

```
1
```
```
11
```
```
21
```
```
1211
```
```
111221
```

循环调用前一次的结果，进行计数。当n=1时，递归结束，返回1.

代码

class Solution {
    public String countAndSay(int n) {
         if (n == 1) {
            return "1";
        }
        String s = countAndSay(n - 1);
        StringBuilder sb = new StringBuilder();
        int cnt = 0;
        for (int i = 0; i < s.length(); i++) {
            if (i == s.length() - 1) {
                cnt++;
                sb.append(cnt).append(s.charAt(i));
            } else if (s.charAt(i) == s.charAt(i + 1)) {
                cnt++;
                continue;
            } else {
                sb.append(cnt+1).append(s.charAt(i));
                cnt=0;
            }
        }
        return sb.toString();
    }
}