Sorting Big Integers

Given a array of n positive integers where each integer can have digits upto 10⁶, print the array elements in ascending order. 

Input: arr[] = {54, 724523015759812365462, 870112101220845, 8723} 
Output: 54 8723 870112101220845 724523015759812365462
Explanation:
All elements of array are sorted in non-descending(i.e., ascending)
order of their integer value

Input: arr[] = {3643641264874311, 451234654453211101231,
                4510122010112121012121}
Output: 3641264874311 451234654453211101231 4510122010112121012121

A naive approach is to use arbitrary precision data type such as int in python or Biginteger class in Java. But that approach will not be fruitful because internal conversion of string to int and then perform sorting will leads to slow down the calculations of addition and multiplications in binary number system.

Python3

# Taking input array
arr = [54, 724523015759812365462, 870112101220845, 8723]

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

# Printing the sorted array
for i in arr:
    print(i)

# Output:
# 54
# 8723
# 870112101220845
# 724523015759812365462

# Note: The sorting is based on lexicographic order, i.e., based on

Javascript

// Taking input array
let arr = [54, 724523015759812365462, 870112101220845, 8723];

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

// Printing the sorted array
for(let i = 0; i < arr.length; i++){
    console.log(arr[i]);
}

Output

54
8723
870112101220845
724523015759812365462

Efficient Solution : As size of integer is very large even it can’t be fit in long long data type of C/C++, so we just need to input all numbers as strings and sort them using a comparison function. Following are the key points compare function:- 

1. If lengths of two strings are different, then we need to compare lengths to decide sorting order.
2. If Lengths are same then we just need to compare both the strings in lexicographically order.

Assumption : There are no leading zeros.

C++

// Below is C++ code to sort the Big integers in
// ascending order
#include<bits/stdc++.h>
using namespace std;

// comp function to perform sorting
bool comp(const string &left, const string &right)
{
    // if length of both string are equals then sort
    // them in lexicographically order
    if (left.size() == right.size())
        return left < right;

    // Otherwise sort them according to the length
    // of string in ascending order
    else
        return left.size() < right.size();
}

// Function to sort arr[] elements according
// to integer value
void SortingBigIntegers(string arr[], int n)
{
    // Copy the arr[] elements to sortArr[]
    vector<string> sortArr(arr, arr + n);

    // Inbuilt sort function using function as comp
    sort(sortArr.begin(), sortArr.end(), comp);

    // Print the final sorted array
    for (auto &ele : sortArr)
        cout << ele << " ";
}

// Driver code of above implementation
int main()
{
    string arr[] = {"54", "724523015759812365462",
                    "870112101220845", "8723"};
    int n = sizeof(arr) / sizeof(arr[0]);

    SortingBigIntegers(arr, n);

    return 0;
}

Java

import java.util.Arrays;
import java.util.Comparator;

public class Main
{

  // comp function to perform sorting
  static class comp implements Comparator<String>
  {
    public int compare(String left, String right)
    {

      // if length of both string are equals then sort
      // them in lexicographically order
      if (left.length() == right.length()) {
        return left.compareTo(right);
      }

      // Otherwise sort them according to the length
      // of string in ascending order
      else {
        return left.length() - right.length();
      }
    }
  }

  // Function to sort arr[] elements according
  // to integer value
  static void SortingBigIntegers(String[] arr, int n)
  {

    // Copy the arr[] elements to sortArr[]
    String[] sortArr = Arrays.copyOf(arr, n);

    // Inbuilt sort function using function as comp
    Arrays.sort(sortArr, new comp());

    // Print the final sorted array
    for (String ele : sortArr) {
      System.out.print(ele + " ");
    }
  }

  // Driver code of above implementation
  public static void main(String[] args) {
    String[] arr = {"54", "724523015759812365462",
                    "870112101220845", "8723"};
    int n = arr.length;

    SortingBigIntegers(arr, n);
  }
}

Python

# Below is Python code to sort the Big integers
# in ascending order
def SortingBigIntegers(arr, n):

  # Direct sorting using lambda operator
  # and length comparison
  arr.sort(key = lambda x: (len(x), x))

# Driver code of above implementation
arr = ["54", "724523015759812365462",
        "870112101220845", "8723"]
n = len(arr)

SortingBigIntegers(arr, n)

# Print the final sorted list using
# join method
print " ".join(arr)

Javascript

<script>
// Below is Javascript code to sort the Big integers in
// ascending order

// comp function to perform sorting
function comp(left, right)
{

    // if length of both string are equals then sort
    // them in lexicographically order
    if (left.length == right.length)
        return left < right;

    // Otherwise sort them according to the length
    // of string in ascending order
    else
        return left.length - right.length;
}

// Function to sort arr[] elements according
// to integer value
function SortingBigIntegers(arr, n)
{

    // Copy the arr[] elements to sortArr[]
    let sortArr = [...arr]

    // Inbuilt sort function using function as comp

    sortArr.sort(comp);

    // Print the final sorted array
    for (ele of sortArr)
        document.write(ele + " ");
}

// Driver code of above implementation
let arr = ["54", "724523015759812365462",
    "870112101220845", "8723"]
let n = arr.length

SortingBigIntegers(arr, n);

// This code is contributed by gfgking.
</script>

C#

using System;
using System.Linq;
using System.Collections.Generic;

public class Program
{
    // comp function to perform sorting
    public class Comp : IComparer<string>
    {
        public int Compare(string left, string right)
        {
            // if length of both string are equals then sort
            // them in lexicographically order
            if (left.Length == right.Length)
            {
                return String.Compare(left, right);
            }

            // Otherwise sort them according to the length
            // of string in ascending order
            else
            {
                return left.Length - right.Length;
            }
        }
    }

    // Function to sort arr[] elements according
    // to integer value
    public static void SortingBigIntegers(string[] arr, int n)
    {

        // Copy the arr[] elements to sortArr[]
        string[] sortArr = (string[])arr.Clone();

        // Inbuilt sort function using function as comp
        Array.Sort(sortArr, new Comp());

        // Print the final sorted array
        foreach (string ele in sortArr)
        {
            Console.Write(ele + " ");
        }
    }

    // Driver code of above implementation
    public static void Main()
    {
        string[] arr = {"54", "724523015759812365462",
                        "870112101220845", "8723"};
        int n = arr.Length;

        SortingBigIntegers(arr, n);
    }
}

Output: 54 8723 870112101220845 724523015759812365462

Time complexity: O(sum * log(n)) where sum is the total sum of all string length and n is size of array 
Auxiliary space: O(n)
Similar Post : 
Sort an array of large numbers
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