Program to generate all possible valid IP addresses from given string | Set 2
Given a string containing only digits, restore it by returning all possible valid IP address combinations.
A valid IP address must be in the form of A.B.C.D, where A, B, C and D are numbers from 0 – 255. The numbers cannot be 0 prefixed unless they are 0.
Examples:
Input: str = “25525511135”
Output:
255.255.11.135
255.255.111.35Input: str = “11111011111”
Output:
111.110.11.111
111.110.111.11
Approach: This problem can be solved using backtracking. In each call we have three options to create a single block of numbers of a valid ip address:
- Either select only a single digit, add a dot and move onto selecting other blocks (further function calls).
- Or select two digits at the same time, add a dot and move further.
- Or select three consecutive digits and move for the next block.
At the end of the fourth block, if all the digits have been used and the address generated is a valid ip-address then add it to the results and then backtrack by removing the digits selected in the previous call.
Below is the implementation of the above approach:
C++
// C++ implementation of the approach #include <iostream> #include <vector> using namespace std; // Function to get all the valid ip-addresses void GetAllValidIpAddress(vector<string>& result, string givenString, int index, int count, string ipAddress) { // If index greater than givenString size // and we have four block if (givenString.size() == index && count == 4) { // Remove the last dot ipAddress.pop_back(); // Add ip-address to the results result.push_back(ipAddress); return; } // To add one index to ip-address if (givenString.size() < index + 1) return; // Select one digit and call the // same function for other blocks ipAddress = ipAddress + givenString.substr(index, 1) + '.'; GetAllValidIpAddress(result, givenString, index + 1, count + 1, ipAddress); // Backtrack to generate another poosible ip address // So we remove two index (one for the digit // and other for the dot) from the end ipAddress.erase(ipAddress.end() - 2, ipAddress.end()); // Select two consecutive digits and call // the same function for other blocks if (givenString.size() < index + 2 || givenString[index] == '0') return; ipAddress = ipAddress + givenString.substr(index, 2) + '.'; GetAllValidIpAddress(result, givenString, index + 2, count + 1, ipAddress); // Backtrack to generate another poosible ip address // So we remove three index from the end ipAddress.erase(ipAddress.end() - 3, ipAddress.end()); // Select three consecutive digits and call // the same function for other blocks if (givenString.size() < index + 3 || stoi(givenString.substr(index, 3)) > 255) return; ipAddress += givenString.substr(index, 3) + '.'; GetAllValidIpAddress(result, givenString, index + 3, count + 1, ipAddress); // Backtrack to generate another poosible ip address // So we remove four index from the end ipAddress.erase(ipAddress.end() - 4, ipAddress.end()); } // Driver code int main() { string givenString = "25525511135"; // Fill result vector with all valid ip-addresses vector<string> result; GetAllValidIpAddress(result, givenString, 0, 0, ""); // Print all the generated ip-addresses for (int i = 0; i < result.size(); i++) { cout << result[i] << "\n"; } } |
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Python3
# Python3 implementation of the approach # Function to get all the valid ip-addresses def GetAllValidIpAddress(result, givenString, index, count, ipAddress) : # If index greater than givenString size # and we have four block if (len(givenString) == index and count == 4) : # Remove the last dot ipAddress.pop(); # Add ip-address to the results result.append(ipAddress); return; # To add one index to ip-address if (len(givenString) < index + 1) : return; # Select one digit and call the # same function for other blocks ipAddress = (ipAddress + givenString[index : index + 1] + ['.']); GetAllValidIpAddress(result, givenString, index + 1, count + 1, ipAddress); # Backtrack to generate another poosible ip address # So we remove two index (one for the digit # and other for the dot) from the end ipAddress = ipAddress[:-2]; # Select two consecutive digits and call # the same function for other blocks if (len(givenString) < index + 2 or givenString[index] == '0') : return; ipAddress = ipAddress + givenString[index:index + 2] + ['.']; GetAllValidIpAddress(result, givenString, index + 2, count + 1, ipAddress); # Backtrack to generate another poosible ip address # So we remove three index from the end ipAddress = ipAddress[:-3]; # Select three consecutive digits and call # the same function for other blocks if (len(givenString)< index + 3 or int("".join(givenString[index:index + 3])) > 255) : return; ipAddress += givenString[index:index + 3] + ['.']; GetAllValidIpAddress(result, givenString, index + 3, count + 1, ipAddress); # Backtrack to generate another poosible ip address # So we remove four index from the end ipAddress = ipAddress[:-4]; # Driver code if __name__ == "__main__" : givenString = list("25525511135"); # Fill result vector with all valid ip-addresses result = [] ; GetAllValidIpAddress(result, givenString, 0, 0, []); # Print all the generated ip-addresses for i in range(len(result)) : print("".join(result[i])); # This code is contributed by Ankitrai01 |
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Output:
255.255.11.135 255.255.111.35
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