Arrange given numbers to form the biggest number | Set 2

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:

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

Input :  [12, 121]
Output : 12121

In SET 1, we have discussed an approach to do same. In this set, we will discuss another logic.

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

// 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 + "]";
    }
}

Python

# Python program to find largest
# number from the given values
# function that return largest
# possible number
def largestNumber(array):

    # extval is a empty list for extended
    # values and ans for calculating answer
    extval, ans = [], ""

    # calculating the length of largest number
    # from given and add 1 for further operation
    l = len(str(max(array))) + 1

    # iterate given values and
    # calculating extended values
    for i in array:
        temp = str(i) * l

        # make tuple of extended value and
        # equivalant original value then
        # append to list
        extval.append((temp[:l:], i))

    # sort extval in descending order
    extval.sort(reverse = True)

    # iterate extended values
    for i in extval:

        # concatinate original value equivalant
        # to extended value into ans variable
        ans += str(i[1])

    if int(ans)==0:
        return "0"
    return ans

# Driver code
a = [1, 34, 3, 98, 9, 76,
        45, 4, 12, 121]

print(largestNumber(a))

# This code is contributed by Chhekur

Output:

99876454343121211

This article is contributed by Kondiparthi Shanmukha Sarath. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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