LeetCode-in-Java
1694. Reformat Phone Number
Easy
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”.t
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”.
Constraints:
2 <= number.length <= 100numberconsists of digits and the characters'-'and' '.- There are at least two digits in
number.
Solution
@SuppressWarnings("java:S135")
public class Solution {
public String reformatNumber(String number) {
StringBuilder sb = new StringBuilder();
for (char c : number.toCharArray()) {
if (Character.isDigit(c)) {
sb.append(c);
}
}
String cleaned = sb.toString();
sb.setLength(0);
int i = 0;
while (i < cleaned.length()) {
if (i + 4 == cleaned.length()) {
sb.append(cleaned, i, i + 2);
sb.append("-");
sb.append(cleaned.substring(i + 2));
break;
} else if (i + 3 <= cleaned.length()) {
sb.append(cleaned, i, i + 3);
sb.append("-");
i += 3;
} else {
sb.append(cleaned.substring(i));
break;
}
}
if (sb.charAt(sb.length() - 1) == '-') {
sb.setLength(sb.length() - 1);
}
return sb.toString();
}
}