1694. Reformat Phone Number

#### QUESTION:

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".
``````

Constraints:

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

#### SOLUTION:

``````class Solution {
func reformatNumber(_ number: String) -> String {
var arr:Array<Character> = []
for num in number {
if (num >= "0" && num <= "9") {
arr.append(num)
}
}
var index = 0
var result = ""
while (index < arr.count) {
if (arr.count - index > 4) {
for _ in 1...3 {
result += String(arr[index])
index += 1
}
result += "-"
} else if (arr.count - index == 4) {
for _ in 1...2 {
result += String(arr[index])
index += 1
}
result += "-"
for _ in 1...2 {
result += String(arr[index])
index += 1
}
} else if (arr.count - index == 3) {
for _ in 1...3 {
result += String(arr[index])
index += 1
}
} else {
for _ in 1...2 {
result += String(arr[index])
index += 1
}
}
}
return result
}
}
``````