Medium · Backtracking

Restore IP Addresses

Given a string digits made only of decimal digits, return every valid IPv4 address that can be formed by inserting exactly three dots into it without reordering or removing digits, in any order; a valid address is four integers 0–255 with no leading zeros (a lone 0 is fine).

{
  "digits": "25525511135"
}

{
  "digits": "0000"
}