Modify array by sorting nearest perfect squares of array elements having their digits sorted in decreasing order

Given an array arr[] of size N (1 ≤ N ≤ 10⁵), the task is to sort digits of each array element in descending order and replace each array element with the nearest perfect square and then print the array in ascending order.

Examples:

Input: arr[ ] = {29, 43, 28, 12}
Output: 25 49 81 100
Explanation:
Sorting digits of each array element in descending order modifies arr[] to {92, 43, 82, 21}.
Replacing elements with the nearest perfect square modifies arr[] to {100, 49, 81, 25}.
Sorting the array in ascending order modifies arr[] to {25, 49, 81, 100}.

Input: arr[ ] = {517, 142, 905}
Output: 441 729 961

Approach: Follow the steps below to solve the problem:

• Traverse the array arr[] and perform the following operations on each array element.
  • Convert them to equivalent string representation.
  • Sort the string in descending order.
  • Convert the string back to its equivalent integer.
  • Find the nearest perfect square of the current array element.
• Now, sort the array in ascending order.
• Print the sorted array.

Below is the implementation of the above approach.

C++

// C++ program of the above approach

#include <bits/stdc++.h>
using namespace std;

// Function to sort array in ascending order
// after replacing array elements by nearest
// perfect square of decreasing order of digits
void sortArr(int arr[], int N)
{

    // Traverse the array of strings
    for (int i = 0; i < N; i++) {

        // Convert the current array
        // element to a string
        string s = to_string(arr[i]);

        // Sort each string in descending order
        sort(s.begin(), s.end(), greater<char>());

        // Convert the string to
        // equivalent integer
        arr[i] = stoi(s);

        // Calculate square root of
        // current array element
        int sr = sqrt(arr[i]);

        // Calculate perfect square
        int a = sr * sr;
        int b = (sr + 1) * (sr + 1);

        // Find the nearest perfect square
        if ((arr[i] - a) < (b - arr[i]))
            arr[i] = a;
        else
            arr[i] = b;
    }

    // Sort the array in ascending order
    sort(arr, arr + N);

    // Print the array
    for (int i = 0; i < N; i++) {
        cout << arr[i] << " ";
    }
}

// Driver Code
int main()
{
    int arr[] = { 29, 43, 28, 12 };
    int N = sizeof(arr) / sizeof(arr[0]);
    sortArr(arr, N);

    return 0;
}

Java

// Java program for the above approach
import java.util.*;

class GFG{
  static void reverse(char[] a)
  {
    int i, n = a.length;
    char t;
    for (i = 0; i < n / 2; i++)
    {
      t = a[i];
      a[i] = a[n - i - 1];
      a[n - i - 1] = t;
    }
  }

  // Function to sort array in ascending order
  // after replacing array elements by nearest
  // perfect square of decreasing order of digits
  static void sortArr(int arr[], int N)
  {

    // Traverse the array of strings
    for (int i = 0; i < N; i++) {

      // Convert the current array
      // element to a string
      String s = Integer.toString(arr[i]);
      char[] str = s.toCharArray();

      // Sort each string in descending order
      Arrays.sort(str);
      reverse(str);

      String string = new String(str);


      // Convert the string to
      // equivalent integer
      arr[i] = Integer.parseInt(string);

      // Calculate square root of
      // current array element
      int sr = (int)Math.sqrt(arr[i]);

      // Calculate perfect square
      int a = sr * sr;
      int b = (sr + 1) * (sr + 1);

      // Find the nearest perfect square
      if ((arr[i] - a) < (b - arr[i]))
        arr[i] = a;
      else
        arr[i] = b;
    }

    // Sort the array in ascending order
    Arrays.sort(arr);

    // Print the array
    for (int i = 0; i < N; i++) {
      System.out.print(arr[i] + " ");
    }
  }


  // Driver Code
  public static void main(String[] args)
  {
    int arr[] = { 29, 43, 28, 12 };
    int N = arr.length;
    sortArr(arr, N);
  }
}

// This code is contributed by sanjoy_62.

Python3

# Python 3 program of the above approach
import math

# Function to sort array in ascending order
# after replacing array elements by nearest
# perfect square of decreasing order of digits
def sortArr(arr, N):

    # Traverse the array of strings
    for i in range(N):

        # Convert the current array
        # element to a string
        s = str(arr[i])

        # Sort each string in descending order
        list1 = list(s)
        list1.sort(reverse = True)
        s = ''.join(list1)

        # Convert the string to
        # equivalent integer
        arr[i] = int(s)

        # Calculate square root of
        # current array element
        sr = int(math.sqrt(arr[i]))

        # Calculate perfect square
        a = sr * sr
        b = (sr + 1) * (sr + 1)

        # Find the nearest perfect square
        if ((arr[i] - a) < (b - arr[i])):
            arr[i] = a
        else:
            arr[i] = b

    # Sort the array in ascending order
    arr.sort()

    # Print the array
    for i in range(N):
        print(arr[i], end=" ")

# Driver Code
if __name__ == "__main__":

    arr = [29, 43, 28, 12]
    N = len(arr)
    sortArr(arr, N)

    # This code is contributed by ukasp.

C#

// C# program of the above approach

using System;
using System.Collections.Generic;

class GFG{

  // Function to sort array in ascending order
  // after replacing array elements by nearest
  // perfect square of decreasing order of digits
  static void sortArr(int []arr, int N)
  {

    // Traverse the array of strings
    for (int i = 0; i < N; i++) {

      // Convert the current array
      // element to a string
      int num = arr[i];
      string s = num.ToString();

      // Sort each string in descending order
      char []temp = s.ToCharArray();
      Array.Sort(temp);
      int st = 0;
      int ed = temp.Length-1;
      while(st<ed){
        char ch = temp[st];
        temp[st] = temp[ed];
        temp[ed] = ch;
        st++;
        ed--;
      }
      string charsStr = new string(temp);
      // sort(s.begin(), s.end(), greater<char>());

      // Convert the string to
      // equivalent integer
      arr[i] = Int32.Parse(charsStr);

      // Calculate square root of
      // current array element
      int sr = (int)Math.Sqrt(arr[i]);

      // Calculate perfect square
      int a = sr * sr;
      int b = (sr + 1) * (sr + 1);

      // Find the nearest perfect square
      if ((arr[i] - a) < (b - arr[i]))
        arr[i] = a;
      else
        arr[i] = b;
    }

    // Sort the array in ascending order
    Array.Sort(arr);

    // Print the array
    for (int i = 0; i < N; i++) {
      Console.Write(arr[i]+" ");
    }
  }

  // Driver Code
  public static void Main()
  {
    int []arr = { 29, 43, 28, 12 };
    int N = arr.Length;
    sortArr(arr, N);

  }
}

// This code is contributed by ipg2016107.

Javascript

<script>

      // JavaScript program of the above approach
      // Function to sort array in ascending order
      // after replacing array elements by nearest
      // perfect square of decreasing order of digits

      function sortArr(arr, N) {
        // Traverse the array of strings
        for (var i = 0; i < N; i++) {
          // Convert the current array
          // element to a string
          var num = arr[i];
          var s = num.toString();

          // Sort each string in descending order
          var temp = s.split("");
          temp.sort((a, b) => b - a);
          s = temp.join("");

          // Convert the string to
          // equivalent integer
          arr[i] = parseInt(s);

          // Calculate square root of
          // current array element
          var sr = parseInt(Math.sqrt(arr[i]));

          // Calculate perfect square
          var a = sr * sr;
          var b = (sr + 1) * (sr + 1);

          // Find the nearest perfect square
          if (arr[i] - a < b - arr[i]) arr[i] = a;
          else arr[i] = b;
        }

        // Sort the array in ascending order
        arr.sort((a, b) => a - b);

        // Print the array
        for (var i = 0; i < N; i++) {
          document.write(arr[i] + " ");
        }
      }

      // Driver Code
      var arr = [29, 43, 28, 12];
      var N = arr.length;
      sortArr(arr, N);

</script>

Output:

25 49 81 100

Time Complexity: O(N*logN+N*M*logM) where N is the size of the array and M is the maximum number of digits present in any element of the array.
Auxiliary Space: O(1)