Create new Mobile Number by selecting maximum from ends after inserting pairwise absolute difference in middle

Given a String ph[], the task is to find the absolute difference of consecutive elements and insert the result in between the consecutive elements. By doing this size of phone numbers will increase from 10 to 19. Now we have to compare digits from first and last and select maximum in this way we will get a new phone number.

Examples:

Input: ph = “9647253846”
Output: 9364857553
Explanation:

Input: ph = “7635892563”
Output: 7363535791

Approach: The idea is to use two pointers approach to solve this problem along with using a string variable to add the phone numbers with a difference. Follow the steps below to solve the problem:

• Initialize a string variable S[] as an empty string.
• Iterate over the range [0, N-1) using the variable i and perform the following tasks:
  • Add ph[i] to the variable S.
  • Initialize the variables s as int(ph[i]) – int(ph[i+1]) and x as abs(s).
  • Add str(x) to the variable S.
• Add ph[9] to the variable S.
• Initialize the variables s as 0 and e as len(S)-1.
• Initialize a string variable ph2[] as an empty string.
• Traverse in a while loop till s is not equals to e and perform the following tasks:
  • Add the max of S[s] or S[e] to the variable ph2[].
  • Increase the value of s by 1 and decrease the value of e by 1.
• Add S[e] to the variable ph2[].
• After performing the above steps, print the value of ph2[] as the answer.

Below is the implementation of the above approach.

C++

// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to create the phone number
string phNumber(string ph, int n)
{

    // Empty string to store extended number
    string S = "";

    // Loop for extend phone number
    for (int i = 0; i < n - 1; i++) {

        // Add character form string
        S += ph[i];

        // Finding absolute difference
        int x = abs(ph[i] - ph[i + 1]);

        // Adding the difference to S
        S += to_string(x);
    }
    // Adding last digit of ph
    S += ph[9];

    // Using 2 pointer algorithm to form comparison

    // s is start index
    int s = 0;

    // e is end index
    int e = S.length() - 1;

    // ph2 an empty string for
    // storing  the phone number
    string ph2 = "";

    // Loop till e become equal to s
    while (s != e) {

        // Comparing element at s and e
        // index and adding maximum

        if (S[s] > S[e]) {
            ph2 += S[s];
        }
        else {
            ph2 += S[e];
        }
        // Increment start index
        s += 1;

        // Decrement end index
        e -= 1;
    }
    // When s = e loop will terminate
    // so adding element at index s = e
    ph2 += S[e];
    // Return phone number
    return ph2;
}

// Driver Code
int main()
{

    // Original phone number
    string ph = "9647253846";

    // Calling function to create new number
    string num = phNumber(ph, ph.length());

    // Print the new number
    cout << num;
}

// This code is contributed by Samim Hossain Mondal.

Java

// Java program for the above approach
class GFG {

  // Function to create the phone number
  static String phNumber(String ph, int n) {

    // Empty string to store extended number
    String S = "";

    // Loop for extend phone number
    for (int i = 0; i < n - 1; i++) {

      // Add character form string
      S += ph.charAt(i);

      // Finding absolute difference
      int x = Math.abs(ph.charAt(i) - ph.charAt(i + 1));

      // Adding the difference to S
      S += Integer.toString(x);
    }
    // Adding last digit of ph
    S += ph.charAt(9);

    // Using 2 pointer algorithm to form comparison

    // s is start index
    int s = 0;

    // e is end index
    int e = S.length() - 1;

    // ph2 an empty string for
    // storing the phone number
    String ph2 = "";

    // Loop till e become equal to s
    while (s != e) {

      // Comparing element at s and e
      // index and adding maximum

      if (S.charAt(s) > S.charAt(e)) {
        ph2 += S.charAt(s);
      } else {
        ph2 += S.charAt(e);
      }
      // Increment start index
      s += 1;

      // Decrement end index
      e -= 1;
    }
    // When s = e loop will terminate
    // so adding element at index s = e
    ph2 += S.charAt(e);
    // Return phone number
    return ph2;
  }

  // Driver Code
  public static void main(String args[]) {

    // Original phone number
    String ph = "9647253846";

    // Calling function to create new number
    String num = phNumber(ph, ph.length());

    // Print the new number
    System.out.println(num);
  }
}

// This code is contributed by gfgking

Python3

# Function to create the phone number
def phNumber(ph, n):

    # Empty string to store extended number
    S =""

    # Loop for extend phone number
    for i in range(n-1):

          # Add character form string
        S+= ph[i]

        # Finding absolute difference
        s = int(ph[i])-int(ph[i + 1])
        x = abs(s)

        # Adding the difference to S
        S+= str(x)

    # Adding last digit of ph
    S+= ph[9]

    # Using 2 pointer algorithm to form comparison

    # s is start index
    s = 0

    # e is end index
    e = len(S)-1

    # ph2 an empty string for
    # storing the phone number
    ph2 =""

    # Loop till e become equal to s
    while s != e:

        # Comparing element at s and e
        # index and adding maximum
        ph2+= max(S[s], S[e])

        # Increment start index
        s+= 1

        # Decrement end index
        e-= 1

    # When s = e loop will terminate
    # so adding element at index s = e
    ph2+= S[e]

    # Return phone number
    return ph2

# Original phone number
ph = "9647253846"

# Calling function to create new number
num = phNumber(ph, len(ph))

# Print the new number
print(num)

C#

// C# program for the above approach
using System;

class GFG {

  // Function to create the phone number
  static string phNumber(string ph, int n)
  {

    // Empty string to store extended number
    string S = "";

    // Loop for extend phone number
    for (int i = 0; i < n - 1; i++) {

      // Add character form string
      S += ph[i];

      // Finding absolute difference
      int x = Math.Abs(ph[i] - ph[i + 1]);

      // Adding the difference to S
      S += x.ToString();
    }
    // Adding last digit of ph
    S += ph[9];

    // Using 2 pointer algorithm to form comparison

    // s is start index
    int s = 0;

    // e is end index
    int e = S.Length - 1;

    // ph2 an empty string for
    // storing the phone number
    string ph2 = "";

    // Loop till e become equal to s
    while (s != e) {

      // Comparing element at s and e
      // index and adding maximum

      if (S[s] > S[e]) {
        ph2 += S[s];
      }
      else {
        ph2 += S[e];
      }
      // Increment start index
      s += 1;

      // Decrement end index
      e -= 1;
    }
    // When s = e loop will terminate
    // so adding element at index s = e
    ph2 += S[e];
    // Return phone number
    return ph2;
  }

  // Driver Code
  public static void Main()
  {

    // Original phone number
    string ph = "9647253846";

    // Calling function to create new number
    string num = phNumber(ph, ph.Length);

    // Print the new number
    Console.Write(num);
  }
}

// This code is contributed by ukasp.

Javascript

<script>
       // JavaScript code for the above approach

       // Function to create the phone number
       function phNumber(ph, n) {

           // Empty string to store extended number
           let S = ""

           // Loop for extend phone number
           for (let i = 0; i < n - 1; i++) {

               // Add character form string
               S += ph[i]

               // Finding absolute difference
               let s = ph[i].charCodeAt(0) - ph[i + 1].charCodeAt(0)
               let x = Math.abs(s)

               // Adding the difference to S
               S += x.toString();
           }
           // Adding last digit of ph
           S += ph[9]

           // Using 2 pointer algorithm to form comparison

           // s is start index
           s = 0

           // e is end index
           e = S.length - 1

           // ph2 an empty string for
           // storing the phone number
           ph2 = ""

           // Loop till e become equal to s
           while (s != e) {

               // Comparing element at s and e
               // index and adding maximum

               if (S[s].charCodeAt(0) > S[e].charCodeAt(0)) {
                   ph2 += S[s];
               }
               else {
                   ph2 += S[e];
               }
               // Increment start index
               s += 1

               // Decrement end index
               e -= 1


           }
           // When s = e loop will terminate
           // so adding element at index s = e
           ph2 += S[e]
           // Return phone number
           return ph2
       }
       // Original phone number
       let ph = "9647253846"

       // Calling function to create new number
       let num = phNumber(ph, ph.length)

       // Print the new number
       document.write(num)

 // This code is contributed by Potta Lokesh
   </script>

Output

9364857553

Time Complexity: O(N)
Auxiliary Space: O(N)