力扣第38题-外观数列

题目
题目链接

题解

常规解法：

class Solution {
    public String countAndSay(int n) {
        String res = "1";
        for(int i = 1; i < n; i++) {
            res = describe(res);
        }
        return res;
    }
    
    private String describe(String described) {
        if (described == null || described.length() == 0) {
            return described;
        }
        StringBuilder des = new StringBuilder();
        for (int i = 0, j = 0; j < described.length(); j++) {
            if (described.charAt(i) != described.charAt(j)) {
                des.append(merge(described.substring(i, j)));
                i = j;
            }
            // 边界处理
            if (j == described.length() - 1) {
                des.append(merge(described.substring(i, j + 1)));
            }
        }
        return des.toString();
    }

    private String merge(String d) {
        return d.length() + d.substring(0, 1);
    }
}

打表解法：没啥意思不写了