g1601_1700.s1694_reformat_phone_number.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated
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package g1601_1700.s1694_reformat_phone_number;

// #Easy #String #2022_04_13_Time_1_ms_(99.67%)_Space_40.7_MB_(88.24%)

/**
 * 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 <= 100`
 * *   `number` consists of digits and the characters `'-'` and `' '`.
 * *   There are at least **two** digits in `number`.
**/
@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();
    }
}