7/16 每日一題(許可證密鑰格式,在第k像加入'-',第一組可無視)

 You are given a license key represented as a string s that consists of only alphanumeric characters and dashes. The string is separated into n + 1 groups by n dashes. You are also given an integer k.

We want to reformat the string s such that each group contains exactly k characters, except for the first group, which could be shorter than k but still must contain at least one character. Furthermore, there must be a dash inserted between two groups, and you should convert all lowercase letters to uppercase.

Return the reformatted license key.

 

Example 1:

Input: s = "5F3Z-2e-9-w", k = 4
Output: "5F3Z-2E9W"
Explanation: The string s has been split into two parts, each part has 4 characters.
Note that the two extra dashes are not needed and can be removed.

Example 2:

Input: s = "2-5g-3-J", k = 2
Output: "2-5G-3J"
Explanation: The string s has been split into three parts, each part has 2 characters except the first part as it could be shorter as mentioned above.

 

Constraints:

• 1 <= s.length <= 105
• s consists of English letters, digits, and dashes '-'.
• 1 <= k <= 104

class Solution:

    def licenseKeyFormatting(self, s: str, k: int) -> str:

        #翻轉字串

        re_s=s[-1::-1].upper().replace('-','')

        i=0 #初始化指針

        res=[] #初始化紀錄用list

        while i < len(re_s):

            if i%k==0 and i != 0:

                res.append('-')

            res.append(re_s[i])

            i+=1

        return ''.join(res[-1::-1])