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Valid IP Addresses

Certification: Intermediate Level Accuracy: 0% Submissions: 0 Points: 12

Write a C# program to restore all possible valid IP addresses from a given string containing only digits. An IP address consists of four decimal numbers separated by dots, each ranging from 0 to 255 inclusive. Leading zeros in decimal numbers are not allowed except for the number 0 itself.

Example 1
    
  
  • Input: "25525511135"
    • 
  
  • Output: ["255.255.11.135", "255.255.111.35"]
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  • Explanation: 
    
      
      
    • There are two ways to split the given string into four valid decimal numbers:
      • 
      
    • 1. 255.255.11.135
      • 
      
    • 2. 255.255.111.35
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    • Both are valid IP addresses.
      • 
    
    
  
    •
Example 2
    
  
  • Input: "0000"
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  • Output: ["0.0.0.0"]
    • 
  
  • Explanation: 
    
      
      
    • There is only one way to split the given string into four valid decimal numbers:
      • 
      
    • 0.0.0.0
      • 
    
    
  
    •
Constraints
    
  
  • 0 ≤ s.length ≤ 20
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  • s consists of digits only
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  • Time Complexity: O(1) since the input is constrained
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  • Space Complexity: O(1) since we generate a finite number of IP addresses
    •
StringsBacktracking TCS (Tata Consultancy Services)Walmart
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Hint
Solution

Solution Hints

    
  
  • Use backtracking to generate all possible combinations
    • 
  
  • Each valid IP address must have exactly 4 segments
    • 
  
  • Each segment must be between 0 and 255 inclusive
    • 
  
  • No leading zeros are allowed (except for 0 itself)
    • 
  
  • Try all possibilities of placing dots between digits
    •

Steps to solve by this approach:

 Step 1: Check if the string length is between 4 and 12, as a valid IP address must have 4 to 12 digits.

 Step 2: Use four nested loops to try all possible combinations of separating the string into four parts.

 Step 3: Ensure that the sum of lengths of all four parts equals the length of the original string.

 Step 4: Parse each part as an integer and verify it's between 0 and 255.

 Step 5: Check for invalid leading zeros in each part (except when the part is just "0").

 Step 6: Construct valid IP addresses and add them to the result list.

 Step 7: Return all possible valid IP addresses found.

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