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Decode the Coding Interview in Scala: Real-World Examples

Restore IP Addresses

Explore techniques to restore valid IP addresses from a string of digits by applying backtracking and constrained programming. Understand how to efficiently validate IP segments and reduce combinations to solve this problem with optimal time and space complexity.

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Description

Given a string s containing only digits, you have to return all the possible IP addresses that can be obtained from the string s in a list.

The order in which IP addresses are placed in the list is not important.

A valid IP address consists of four integers, where each integer lies within the range of 0 and 255. These integers are separated by single dots . and cannot have leading zeros.

Constraints

  • The input string s consists of digits only.
  • 4 <= s.length <= 12

Let’s review a few examples below:

Coding exercise

Scala
object Solution
{
  def restoreIpAddresses(s:String):Array[String]= {
    //Write your code here
    return Array("-")
  };
}
Restore IP Addresses

Solution

The naive brute force solution would be to check all possible positions of the dots and only keep the valid ones. We have 11 possible positions where we can place the dots. For the first dot ., we will have 11 possible positions, 10 for the ...