# Greatest number that can be formed from a pair in a given Array

• Last Updated : 10 Nov, 2021

Given an array arr[], the task is to find the largest number that can be formed from a pair in the given array.
Examples:

Input: arr[] = { 3, 1, 9, 2 }
Output: 93
The pair (3, 9) leads to forming of maximum number 93
Input: arr[] = { 23, 14, 16, 25, 3, 9 }
Output: 2523
The pair (23, 25) leads to forming of maximum number 2523

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Approach: The idea is to form every possible pairs of the array. Then for each pair X and Y, join them as XY and YX and take the maximum out of all such pairs.

for every possible in array (X, Y)

Below is the implementation of the above approach:

## C++

 `// C++ implementation to find the``// greatest number from the``// given pairs of the array` `#include ``using` `namespace` `std;` `// Function to find the greatest``// number formed from the pairs``string getNumber(``int` `a, ``int` `b)``{``    ``string X = to_string(a);``    ``string Y = to_string(b);` `    ``// 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 than other``    ``return` `XY > YX ? XY : YX;``}` `// Function to find pairs from array``void` `printMaxPair(``int` `arr[], ``int` `n)``{``    ``int` `largest = INT_MIN;` `    ``// Iterate through all pairs``    ``for` `(``int` `i = 0; i < n; i++)``        ``for` `(``int` `j = i + 1; j < n; j++) {``            ``int` `number = stoi(``                ``getNumber(arr[i], arr[j]));``            ``largest = max(largest, number);``        ``}``    ``cout << largest;``}` `// Driver code``int` `main()``{``    ``int` `a[] = { 23, 14, 16, 25, 3, 9 };``    ``int` `n = ``sizeof``(a) / ``sizeof``(a[0]);``    ``printMaxPair(a, n);``    ``return` `0;``}`

## Java

 `// Java implementation to find the``// greatest number from the``// given pairs of the array``import` `java.util.*;` `class` `GFG{` `// Function to find the greatest``// number formed from the pairs``static` `String getNumber(``int` `a, ``int` `b)``{``    ``String X = Integer.toString(a);``    ``String Y = Integer.toString(b);` `    ``// 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 than other``    ``return` `XY.compareTo(YX) > ``0` `? XY : YX;``    ` `}` `// Function to find pairs from array``static` `void` `printMaxPair(``int` `arr[], ``int` `n)``{``    ``int` `largest = Integer.MIN_VALUE;` `    ``// Iterate through all pairs``    ``for``(``int` `i = ``0``; i < n; i++)``       ``for``(``int` `j = i + ``1``; j < n; j++)``       ``{``          ``int` `number = Integer.parseInt(getNumber(arr[i],``                                                  ``arr[j]));``          ``largest = Math.max(largest, number);``       ``}``       ``System.out.println(largest);``}` `// Driver code``public` `static` `void` `main(String[] args)``{``    ``int` `a[] = { ``23``, ``14``, ``16``, ``25``, ``3``, ``9` `};``    ``int` `n = a.length;``    ` `    ``printMaxPair(a, n);``}``}` `// This code is contributed by offbeat`

## Python3

 `# Python3 implementation to find the``# greatest number from the``# given pairs of the array``import` `sys;` `# Function to find the greatest``# number formed from the pairs``def` `getNumber(a, b):` `    ``X ``=` `str``(a);``    ``Y ``=` `str``(b);` `    ``# first append Y at``    ``# the end of X``    ``XY ``=` `X ``+` `Y;` `    ``# then append X at``    ``# the end of Y``    ``YX ``=` `Y ``+` `X;` `    ``# Now see which of the``    ``# two formed numbers``    ``# is greater than other``    ``if``(XY > YX):``        ``return` `XY;``    ``else``:``        ``return` `YX;` `# Function to find pairs from array``def` `printMaxPair(arr, n):` `    ``largest ``=` `-``sys.maxsize ``-` `1``;` `    ``# Iterate through all pairs``    ``for` `i ``in` `range``(``0``, n):``        ``for` `j ``in` `range``(i ``+` `1``, n):``            ``number ``=` `int``(getNumber(arr[i],``                                   ``arr[j]));``            ``largest ``=` `max``(largest, number);``        ` `    ``print``(largest);` `# Driver code``a ``=` `[ ``23``, ``14``, ``16``, ``25``, ``3``, ``9` `];``n ``=` `len``(a);``printMaxPair(a, n);` `# This code is contributed by Code_Mech`

## C#

 `// C# implementation to find the``// greatest number from the``// given pairs of the array``using` `System;` `class` `GFG{` `// Function to find the greatest``// number formed from the pairs``static` `String getNumber(``int` `a, ``int` `b)``{``    ``String X = a.ToString();``    ``String Y = b.ToString();` `    ``// 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 than other``    ``return` `XY.CompareTo(YX) > 0 ? XY : YX;``    ` `}` `// Function to find pairs from array``static` `void` `printMaxPair(``int` `[]arr, ``int` `n)``{``    ``int` `largest = ``int``.MinValue;` `    ``// Iterate through all pairs``    ``for``(``int` `i = 0; i < n; i++)``       ``for``(``int` `j = i + 1; j < n; j++)``       ``{``          ``int` `number = Int32.Parse(getNumber(arr[i],``                                             ``arr[j]));``          ``largest = Math.Max(largest, number);``       ``}``       ``Console.WriteLine(largest);``}` `// Driver code``public` `static` `void` `Main(String[] args)``{``    ``int` `[]a = { 23, 14, 16, 25, 3, 9 };``    ``int` `n = a.Length;``    ` `    ``printMaxPair(a, n);``}``}` `// This code is contributed by Amit Katiyar`

## Javascript

 ``
Output:
`2523`

Time Complexity: O(n2)

Auxiliary Space: O(1)

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