[daily 3 questions (3)] reformat the phone number

2 Brother ：3 Sister , Stop watching soap operas , Today, let's do an algorithm problem .

3 Sister turned off the TV , Happy to run over .
3 Sister ： Yes, yes ,java I have learned all the data structures of , Let's just put the horse here .

subject ：

Give you a phone number in string form number .number By digital 、 Space ’ '、 And dash ‘-’ form .

Please reformat the phone number as follows .

First , Delete All the spaces and dashes .
secondly , Move the array from left to right Every time 3 In groups Block , until be left over 4 Number or less . The remaining numbers will be subdivided as follows ：
2 A digital ： Single containing 2 A block of numbers .
3 A digital ： Single containing 3 A block of numbers .
4 A digital ： The two contain 2 A block of numbers .
Finally, we use dashes to connect the blocks . Be careful , During reformatting Should not be Generation contains only 1 A block of numbers , also most Generate two with 2 A block of numbers .

Returns the formatted phone number .

Example 1：

Input ：number = “1-23-45 6”
Output ：“123-456”
explain ： The number is “123456”
step 1： More than 4 A digital , So take it first 3 There are numbers in a group . The first 1 The block is “123” .
step 2： be left over 3 A digital , Put them in a single containing 3 A block of numbers . The first 2 The block is “456” .
Join these blocks and you get “123-456” .
Example 2：

Input ：number = “123 4-567”
Output ：“123-45-67”
explain ： The number is “1234567”.
step 1： More than 4 A digital , So take it first 3 There are numbers in a group . The first 1 The block is “123” .
step 2： be left over 4 A digital , So divide them into two parts 2 A block of numbers . this 2 The blocks are “45” and “67” .
Join these blocks and you get “123-45-67” .
Example 3：

Input ：number = “123 4-5678”
Output ：“123-456-78”
explain ： The number is “12345678” .
step 1： The first 1 Block “123” .
step 2： The first 2 Block “456” .
step 3： be left over 2 A digital , Put them in a single containing 2 A block of numbers . The first 3 The block is “78” .
Join these blocks and you get “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”

Tips ：

2 <= number.length <= 100
number By numbers and characters ‘-’ And ’ ’ form .
number It contains at least 2 A digital .

java Code ：

class Solution {
    public String reformatNumber(String number) {
        number = number.replace(" ", "");
        number = number.replace("-", "");

        int n = number.length();
        StringBuilder sbd = new StringBuilder();
        if(n <=3) {
            sbd.append(number);
            return sbd.toString();
        }
        
        int duan = n/3;
        int yu = n%3;

        for(int i=0;i<duan-1;i++) {
            sbd.append(number.substring(3*i, 3*i+3)).append("-");
        }

        if(yu ==0) {
            sbd.append(number.substring(n-3));
        }else if(yu == 1) {
            sbd.append(number.substring(n-4, n-2)).append("-").append(number.substring(n-2));
        }else {
            sbd.append(number.substring(n-5, n-2)).append("-").append(number.substring(n-2));
        }

        return sbd.toString();
    }
}