1694. Reformat Phone Number

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".

Example 4:

Input: number = "12"
Output: "12"

Example 5:

Input: number = "--17-5 229 35-39475 "
Output: "175-229-353-94-75"

Constraints:

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

1694. Reformat Phone Number
struct Solution;

impl Solution {
fn reformat_number(number: String) -> String {
let nums: Vec<char> = number
.chars()
.filter(|&c| ('0'..='9').contains(&c))
.collect();
let mut res = "".to_string();
let n = nums.len();
let mut i = 0;
while n - i > 4 {
res.push(nums[i]);
i += 1;
res.push(nums[i]);
i += 1;
res.push(nums[i]);
i += 1;
res.push('-');
}
if n - i == 4 {
res.push(nums[i]);
i += 1;
res.push(nums[i]);
i += 1;
res.push('-');
res.push(nums[i]);
i += 1;
res.push(nums[i]);
} else {
while n - i > 0 {
res.push(nums[i]);
i += 1;
}
}
res
}
}

#[test]
fn test() {
let number = "1-23-45 6".to_string();
let res = "123-456".to_string();
assert_eq!(Solution::reformat_number(number), res);
let number = "123 4-567".to_string();
let res = "123-45-67".to_string();
assert_eq!(Solution::reformat_number(number), res);
let number = "123 4-5678".to_string();
let res = "123-456-78".to_string();
assert_eq!(Solution::reformat_number(number), res);
let number = "12".to_string();
let res = "12".to_string();
assert_eq!(Solution::reformat_number(number), res);
let number = "--17-5 229 35-39475 ".to_string();
let res = "175-229-353-94-75".to_string();
assert_eq!(Solution::reformat_number(number), res);
}