Find All Possible IP Addresses After Restoration in C++

Suppose we have a string with only digits, we have to restore it by forming all possible valid IP address combinations. We know that a valid IP address consists of exactly four integers (each integer is in range 0 to 255) separated by single period symbol.

So, if the input is like ip = "25525511136", then the output will be ["254.25.40.123", "254.254.0.123"]

To solve this, we will follow these steps −

• Define a function convertToNum(), this will take s, start, end,
• num := 0
• for initialize i := start, when i <= end, update (increase i by 1), do −
  • num := (num * 10) + (s[i] - ASCII of '0')
  • if num > 255, then −
    • return 10000
• return num
• Define a function addDots(), this will take positions,
• res := blank string
• x := 0, posIndex := 0
• for initialize i := 0, when i < size of positions, update (increase i by 1), do −
  • num := positions[i]
  • create one string str1
  • temp := num as string
  • res := res + temp
  • if i < size of positions, then −
    • res := res concatenate "."
• return res
• Define a function solve(), this will take s, one string array result, an array positions, dotCount, this is initialize it with 3, startIndex, this is initialize it with 0,
• if not dotCount is non-zero and ((size of s - 1) - startIndex + 1) 1, then −
  • temp := convertToNum(s, startIndex, size of s)
  • if temp >= 0 and temp <= 255, then −
    • insert temp at the end of positions
    • res := addDots(positions)
    • if size of res is same as size of s, then −
      • insert res at the end of result
  • return
• for initialize i := startIndex, when i < size of s, update (increase i by 1), do −
  • temp := convertToNum(s, startIndex, i)
  • if temp >= 0 and temp <= 255, then −
    • insert temp at the end of positions
    • solve(s, result, positions, dotCount - 1, i + 1)
    • delete last element from positions
• Define one function genIp this will take a string s
• Define an array result
• Define an array position
• solve(s, result, position)
• return result
• From the main method call genIp(A)

Example (C++)

Let us see the following implementation to get better understanding −

 Live Demo

#include <bits/stdc++.h>
using namespace std;
void print_vector(vector<auto> v){
   cout << "[";
   for(int i = 0; i<v.size(); i++){
      cout << v[i] << ", ";
   }
   cout << "]"<<endl;
}
typedef long long int lli;
class Solution {
   public:
   lli convertToNum(string s,int start, int end){
      lli num = 0;
      for (int i = start; i <= end; i++) {
         num = (num * 10) + (s[i] - '0');
         if (num > 255)
            return 10000;
      }
      return num;
   }
   string addDots(vector <int> positions){
      string res = "";
      int x = 0;
      int posIndex = 0;
      for (int i = 0; i < positions.size(); i++) {
         int num = positions[i];
         ostringstream str1;
         str1 << num;
         string temp = str1.str();
         res += temp;
         if (i < positions.size() - 1)
            res += ".";
         }
         return res;
      }
      void solve(string s, vector <string> &result,vector <int> positions, int dotCount = 3, int startIndex = 0){
         if (!dotCount && ((s.size() - 1) - startIndex + 1) >= 1) {
            int temp = convertToNum(s, startIndex, s.size() - 1);
            if (temp >= 0 && temp <= 255) {
               positions.push_back(temp);
               string res = addDots(positions);
               if (res.size() - 3 == s.size()) {
                  result.push_back(res);
            }
         }
         return;
      }
      for (int i = startIndex; i < s.size(); i++) {
         int temp = convertToNum(s, startIndex, i);
         if (temp >= 0 && temp <= 255) {
            positions.push_back(temp);
            solve(s, result, positions, dotCount - 1, i + 1);
            positions.pop_back();
         }
      }
   }
   vector<string> genIp(string s){
   vector<string> result;
   vector<int> position;
   solve(s, result, position);
   return result;
   }
   vector<string> get_ip(string A) {
   return genIp(A);
}};
main(){
   Solution ob;
   string ip = "25525511136";
   print_vector(ob.get_ip(ip));
}

Input

25525511136

Output

[255.255.11.136, 255.255.111.36, ]