重新格式化电话号码

/*
 * 思路：
 * 1. 删除所有空格和破折号
 * 2. 按照每3个数字分组，直到剩下4个或更少的数字
 * 3. 如果剩下4个数字，将其分为两个含2个数字的块
 * 4. 用破折号连接这些块
 */

import java.util.stream.Collectors;

public class Solution {
    public String reformatNumber(String number) {
        // Step 1: Remove all spaces and dashes
        String cleaned = number.chars()
                               .filter(Character::isDigit)
                               .mapToObj(c -> String.valueOf((char) c))
                               .collect(Collectors.joining());
        StringBuilder result = new StringBuilder();
        int length = cleaned.length();
        int index = 0;

        // Step 2: Process the main part of the string
        while (length > 4) {
            result.append(cleaned, index, index + 3).append("-");
            index += 3;
            length -= 3;
        }

        // Step 3: Handle the remaining part of the string
        if (length == 4) {
            result.append(cleaned, index, index + 2).append("-")
                  .append(cleaned, index + 2, index + 4);
        } else { // length is 2 or 3
            result.append(cleaned, index, cleaned.length());
        }

        return result.toString();
    }
}