Restore IP Addresses in C++

Suppose we have a string containing only digits, we have to restore it by returning 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 points.

So, if the input is like "25525511135", then the output will be ["255.255.11.135", "255.255.111.35"]

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

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> restoreIpAddresses(string A) {
   return genIp(A);
}};
main(){
   Solution ob;
   print_vector(ob.restoreIpAddresses("25525511135"));
}