Form the biggest number - 2

Software Development
#1

Given an array of non-negative numbers(of Integer Range), they are needed to be arranged in some order such that it gives the max number. For example given array is A[1, 34, 3, 98, 9, 76, 45, 4, 12, 121]. if we arrange these numbers in the following order, A[9, 98, 76, 45, 4, 34, 3, 12, 121, 1], then by joining them we get “99876454343121211” as largest number.

Examples:

  1. Find number of digits in the largest number. Let number of digits be n.
  2. Create extended version of all numbers. In extended version, we have n+1 digits formed by concatenating the number of with itself and truncating extra digits.
  3. Sort original numbers according to their extended values.
  4. Concatenating the sorted numbers produces th required result.

// Java program to arrange the numbers to form the

// largest number

import java.math.BigInteger;

import java.util.*;

public class LargestNumber

{

// method that returns largest number form

public static String largestNumber(List<Integer> arr)

{

// finding number of digits in maximum element

// present in array

int n =

Collections.max(arr).toString().length();

ArrayList<ExtendedNum> en =

new ArrayList<ExtendedNum>();

for ( int i = 0 ; i < arr.size(); i++)

en.add( new ExtendedNum(arr.get(i),

n));

// sort based on modified value

Collections.sort(en, (p1, p2) ->

( int )(p2.modifiedValue - p1.modifiedValue));

StringBuilder sb = new StringBuilder();

for ( int i = 0 ; i < en.size(); i++)

sb.append( new StringBuilder

(Long.toString(en.get(i).originalValue)));

// To remove any zeroes at head.

BigInteger bi = new BigInteger(sb.toString());

return bi.toString();

}

// Driver method

public static void main(String[] args)

{

Integer arr[] = { 1 , 34 , 3 , 98 , 9 , 76 , 45 ,

4 , 12 , 121 };

List<Integer> l = Arrays.asList(arr);

System.out.println(largestNumber(l));

}

}

// A utility class to generate new value

class ExtendedNum

{

int originalValue;

long modifiedValue;

public ExtendedNum( int originalValue, int n)

{

this .originalValue = originalValue;

String s = Integer.toString(originalValue);

StringBuilder sb = new StringBuilder(s);

StringBuilder ans = new StringBuilder();

while (ans.length() <= n + 1 )

ans.append(sb);

s = ans.toString().substring( 0 , n + 1 );

modifiedValue = Long.parseLong(s);

}

public String toString()

{

return "[" + modifiedValue +

", " + originalValue + "]" ;

}

}

Output:

99876454343121211
Input : [1, 34, 3, 98, 9, 76, 45, 4, 12, 121] Output : 99876454343121211 Input : [12, 121] Output : 12121