You are given a phone number as a string number. number consists of digits, spaces ' ', and/or dashes '-'.

You would like to reformat the phone number in a certain manner. Firstly, remove all spaces and dashes. Then, group the digits from left to right into blocks of length 3 until there are 4 or fewer digits. The final digits are then grouped as follows:

• 2 digits: A single block of length 2.
• 3 digits: A single block of length 3.
• 4 digits: Two blocks of length 2 each.

The blocks are then joined by dashes. Notice that the reformatting process should never produce any blocks of length 1 and produce at most two blocks of length 2.

Return the phone number after formatting.

Example 1:

Input: number = "1-23-45 6" Output: "123-456" Explanation: The digits are "123456". Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123". Step 2: There are 3 digits remaining, so put them in a single block of length 3. The 2nd block is "456". Joining the blocks gives "123-456". 

Example 2:

Input: number = "123 4-567" Output: "123-45-67" Explanation: The digits are "1234567". Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123". Step 2: There are 4 digits left, so split them into two blocks of length 2. The blocks are "45" and "67". Joining the blocks gives "123-45-67". 

Example 3:

Input: number = "123 4-5678" Output: "123-456-78" Explanation: The digits are "12345678". Step 1: The 1st block is "123". Step 2: The 2nd block is "456". Step 3: There are 2 digits left, so put them in a single block of length 2. The 3rd block is "78". Joining the blocks gives "123-456-78". 

Example 4:

Input: number = "12" Output: "12" 

Example 5:

Input: number = "--17-5 229 35-39475 " Output: "175-229-353-94-75" 

Constraints:

• 2 <= number.length <= 100
• number consists of digits and the characters '-' and ' '.
• There are at least two digits in number.

给你一个字符串形式的电话号码 number 。number 由数字、空格 ' '、和破折号 '-' 组成。

请你按下述方式重新格式化电话号码。

• 首先，删除 所有的空格和破折号。
• 其次，将数组从左到右 每 3 个一组 分块，直到 剩下 4 个或更少数字。剩下的数字将按下述规定再分块：
  • 2 个数字：单个含 2 个数字的块。
  • 3 个数字：单个含 3 个数字的块。
  • 4 个数字：两个分别含 2 个数字的块。

最后用破折号将这些块连接起来。注意，重新格式化过程中 不应该 生成仅含 1 个数字的块，并且 最多 生成两个含 2 个数字的块。返回格式化后的电话号码。

• 简单题。先判断号码是不是 2 位和 4 位，如果是，单独输出这 2 种情况。剩下的都是 3 位以上了，取余，判断剩余的数字是 2 个还是 4 个。这时不可能存在剩 1 位数的情况。除 3 余 1，即剩 4 位的情况，末尾 4 位需要 2 个一组输出。除 3 余 2，即剩 2 位的情况。处理好末尾，再逆序每 3 个一组连接 "-" 即可。可能需要注意的 case 见 test 文件。

package leetcode import ( "strings" ) funcreformatNumber(numberstring) string { parts, nums:= []string{}, []rune{} for_, r:=rangenumber { ifr!='-'&&r!=' ' { nums=append(nums, r) } } threeDigits, twoDigits:=len(nums)/3, 0switchlen(nums) %3 { case1: threeDigits--twoDigits=2case2: twoDigits=1default: twoDigits=0 } fori:=0; i<threeDigits; i++ { s:=""s+=string(nums[0:3]) nums=nums[3:] parts=append(parts, s) } fori:=0; i<twoDigits; i++ { s:=""s+=string(nums[0:2]) nums=nums[2:] parts=append(parts, s) } returnstrings.Join(parts, "-") }