Arrange given numbers to form the biggest number | Set 1

Given an array of numbers, arrange them in a way that yields the largest value. For example, if the given numbers are {54, 546, 548, 60}, the arrangement 6054854654 gives the largest value. And if the given numbers are {1, 34, 3, 98, 9, 76, 45, 4}, then the arrangement 998764543431 gives the largest value.

A simple solution that comes to our mind is to sort all numbers in descending order, but simply sorting doesn’t work. For example, 548 is greater than 60, but in output 60 comes before 548. As a second example, 98 is greater than 9, but 9 comes before 98 in output.

So how do we go about it? The idea is to use any comparison based sorting algorithm. In the used sorting algorithm, instead of using the default comparison, write a comparison function myCompare() and use it to sort numbers. Given two numbers X and Y, how should myCompare() decide which number to put first – we compare two numbers XY (Y appended at the end of X) and YX (X appended at the end of Y). If XY is larger, then X should come before Y in output, else Y should come before. For example, let X and Y be 542 and 60. To compare X and Y, we compare 54260 and 60542. Since 60542 is greater than 54260, we put Y first.

Following is the implementation of the above approach. To keep the code simple, numbers are considered as strings, and vector is used instead of normal array.

C++

filter_none

edit
close

play_arrow

link
brightness_4
code

// Given an array of numbers, program to arrange the numbers to form the
// largest number
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
  
// A comparison function which is used by sort() in printLargest()
int myCompare(string X, string Y)
{
    // first append Y at the end of X
    string XY = X.append(Y);
  
    // then append X at the end of Y
    string YX = Y.append(X);
  
    // Now see which of the two formed numbers is greater
    return XY.compare(YX) > 0 ? 1: 0;
}
  
// The main function that prints the arrangement with the largest value.
// The function accepts a vector of strings
void printLargest(vector<string> arr)
{
    // Sort the numbers using library sort funtion. The function uses
    // our comparison function myCompare() to compare two strings.
    // See http://www.cplusplus.com/reference/algorithm/sort/ for details
    sort(arr.begin(), arr.end(), myCompare);
  
    for (int i=0; i < arr.size() ; i++ )
        cout << arr[i];
}
  
// driver program to test above functions
int main()
{
    vector<string> arr;
  
    //output should be 6054854654
    arr.push_back("54");
    arr.push_back("546");
    arr.push_back("548");
    arr.push_back("60");
    printLargest(arr);
  
    // output should be 777776
    /*arr.push_back("7");
    arr.push_back("776");
    arr.push_back("7");
    arr.push_back("7");*/
  
    //output should be 998764543431
    /*arr.push_back("1");
    arr.push_back("34");
    arr.push_back("3");
    arr.push_back("98");
    arr.push_back("9");
    arr.push_back("76");
    arr.push_back("45");
    arr.push_back("4");
    */
  
   return 0;
}

chevron_right






                        filter_none









Java














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















// Given an array of numbers, program to 


// arrange the numbers to form the  


// largest number 


import java.util.*; 


  


class GFG { 


  


    // The main function that prints the  


    // arrangement with the largest value. 


    // The function accepts a vector of strings     


    static void printLargest(Vector<String> arr){ 


      


        Collections.sort(arr, new Comparator<String>(){ 


  


        // A comparison function which is used by  


        // sort() in printLargest() 


        @Override


        public int compare(String X, String Y) { 


          


        // first append Y at the end of X 


        String XY=X + Y; 


          


        // then append X at the end of Y 


        String YX=Y + X; 


          


        // Now see which of the two formed numbers  


        // is greater 


        return XY.compareTo(YX) > 0 ? -1:1; 


    } 


    }); 


          


    Iterator it = arr.iterator(); 


  


    while(it.hasNext()) 


        System.out.print(it.next()); 


      


    } 


      


    // driver program 


    public static void main (String[] args) { 


          


        Vector<String> arr; 


        arr = new Vector<>(); 


          


        //output should be 6054854654 


        arr.add("54"); 


        arr.add("546"); 


        arr.add("548"); 


        arr.add("60"); 


        printLargest(arr); 


         


        // output should be 777776 


        /* arr.add("7"); 


        arr.add("776"); 


        arr.add("7"); 


        arr.add("7"); 


        */


          


        //output should be 998764543431 


        /*arr.add("1"); 


        arr.add("34"); 


        arr.add("3"); 


        arr.add("98"); 


        arr.add("9"); 


        arr.add("76"); 


        arr.add("45"); 


        arr.add("4"); 


        */


    } 


} 


// This code is contributed by Shubham Juneja 



















                        chevron_right







                        filter_none









Python3














                                    filter_none




                                    edit

                                    close




                                    play_arrow




                                    link

                                    brightness_4

                                    code
                                




















# Python3 Program to get the maximum 


# possible integer from given array 


# of integers... 


  


  


# custom comparator to sort according 


# to the ab, ba as mentioned in description 


def comparator(a, b): 


    ab = str(a) + str(b) 


    ba = str(b) + str(a) 


    return ((int(ba) > int(ab)) - (int(ba) < int(ab))) 


      


def myCompare(mycmp): 


      


    # Convert a cmp= function into a key= function 


    class K(object): 


        def __init__(self, obj, *args): 


            self.obj = obj 


        def __lt__(self, other): 


            return mycmp(self.obj, other.obj) < 0


        def __gt__(self, other): 


            return mycmp(self.obj, other.obj) > 0


        def __eq__(self, other): 


            return mycmp(self.obj, other.obj) == 0


        def __le__(self, other): 


            return mycmp(self.obj, other.obj) <= 0


        def __ge__(self, other): 


            return mycmp(self.obj, other.obj) >= 0


        def __ne__(self, other): 


            return mycmp(self.obj, other.obj) != 0


    return K 


# driver code 


if __name__ == "__main__": 


    a = [54, 546, 548, 60, ] 


    sorted_array = sorted(a, key=myCompare(comparator)) 


    number = "".join([str(i) for i in sorted_array]) 


    print(number) 


  


# This code is Contributed by SaurabhTewary 



















                        chevron_right







                        filter_none










Output: 


6054854654


This article is compiled by Ravi Chandra Enaganti. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



          
          
          
          

            

    

        My Personal Notes
        arrow_drop_up
    

    

        
        

            
            
        

    


Recommended Posts:

Improved By :  SaurabhTewary