Related Articles
Largest lexicographic triplet from a given Array that forms a triangle
• Last Updated : 03 Aug, 2020

Given an array arr[], the task is to find the lexicographically largest triplet in that array that can form a triangle. If no such triplet exists, print -1.
Example:

Input: arr[] = { 4, 2, 10, 3, 5 }
Output: 3 4 5
Explanation:
The lexicographically largest triplet is (4, 5, 10). But it does not form a triangle.
The next lexicographically largest triplet is (3, 4, 5).
Since it forms a triangle, it is the required answer.
Input: arr[] = { 20, 12, 120, 3, 15 }
Output: 12 15 20

Approach:
A triplet can form a triangle if and only if it follows the condition given below:

If A, B and C forms a triplet, then the triplet can form a triangle if
A < B + C or B < A + C or C < A + B

The idea is to use Sorting. Sort the array in ascending order. Start traversing from the end of the array and check if any triplet satisfies the above condition. Print the first triplet to satisfy the condition, as the output. If no such triplet can be found, then print -1.
Below is the implementation of the above approach:

## C++

 `// C++ Program to implement``// the the above approach``#include ``using` `namespace` `std;` `// Function to find lexicographically``// largest triplet that forms a``// triangle in the given array``void` `findTriplet(``int` `arr[], ``int` `N)``{` `    ``// Sort the array``    ``sort(arr, arr + N);` `    ``int` `flag = 0, i;` `    ``// Iterate from the end of the array``    ``for` `(i = N - 1; i - 2 >= 0; i--) {` `        ``// If the triplet forms a triangle``        ``if` `(arr[i - 2] + arr[i - 1] > arr[i]) {``            ``flag = 1;``            ``break``;``        ``}``    ``}` `    ``// If triplet found``    ``if` `(flag) {` `        ``// Print the triplet``        ``cout << arr[i - 2] << ``" "``             ``<< arr[i - 1] << ``" "``             ``<< arr[i] << endl;``    ``}` `    ``// Otherwise``    ``else` `{``        ``cout << -1 << endl;``    ``}``}` `// Driver Code``int` `main()``{``    ``int` `arr[] = { 4, 2, 10, 3, 5 };` `    ``int` `N = ``sizeof``(arr) / ``sizeof``(arr);` `    ``findTriplet(arr, N);` `    ``return` `0;``}`

## Java

 `// Java program to implement``// the the above approach``import` `java.util.*;` `class` `GFG{``    ` `// Function to find lexicographically``// largest triplet that forms a``// triangle in the given array``static` `void` `findTriplet(``int` `arr[], ``int` `N)``{``    ` `    ``// Sort the array``    ``Arrays.sort(arr);` `    ``int` `flag = ``0``, i;` `    ``// Iterate from the end of the array``    ``for``(i = N - ``1``; i - ``2` `>= ``0``; i--)``    ``{``        ` `        ``// If the triplet forms a triangle``        ``if` `(arr[i - ``2``] + arr[i - ``1``] > arr[i])``        ``{``            ``flag = ``1``;``            ``break``;``        ``}``    ``}` `    ``// If triplet found``    ``if` `(flag != ``0``)``    ``{``        ` `        ``// Print the triplet``        ``System.out.println(arr[i - ``2``] + ``" "` `+``                           ``arr[i - ``1``] + ``" "` `+``                           ``arr[i] );``    ``}` `    ``// Otherwise``    ``else``    ``{``        ``System.out.println(-``1``);``    ``}``}` `// Driver Code``public` `static` `void` `main (String []args)``{``    ``int` `arr[] = { ``4``, ``2``, ``10``, ``3``, ``5` `};` `    ``int` `N = arr.length;` `    ``findTriplet(arr, N);``}``}` `// This code is contributed by chitranayal`

## Python3

 `# Python3 implementation of``# the above approach` `# Function to find lexicographically``# largest triplet that forms a``# triangle in the given array``def` `findTriplet(arr, N):` `    ``# Sort the array``    ``arr.sort()` `    ``# Iterate from the end of the array``    ``i ``=` `N ``-` `1``    ``while` `i ``-` `2` `>``=` `0``:` `        ``# If the triplet forms a triangle``        ``if``(arr[i ``-` `2``] ``+` `arr[i ``-` `1``] > arr[i]):``            ``flag ``=` `1``            ``break` `        ``i ``-``=` `1` `    ``# If triplet found``    ``if``(flag):` `        ``# Print the triplet``        ``print``(arr[i ``-` `2``],``              ``arr[i ``-` `1``],``              ``arr[i])` `    ``# Otherwise``    ``else``:``        ``print``(``-``1``)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:` `    ``arr ``=` `[ ``4``, ``2``, ``10``, ``3``, ``5` `]` `    ``N ``=` `len``(arr)` `    ``findTriplet(arr, N)` `# This code is contributed by Shivam Singh`

## C#

 `// C# program to implement``// the the above approach``using` `System;``class` `GFG{``    ` `// Function to find lexicographically``// largest triplet that forms a``// triangle in the given array``static` `void` `findTriplet(``int` `[]arr, ``int` `N)``{``    ` `    ``// Sort the array``    ``Array.Sort(arr);` `    ``int` `flag = 0, i;` `    ``// Iterate from the end of the array``    ``for``(i = N - 1; i - 2 >= 0; i--)``    ``{``        ` `        ``// If the triplet forms a triangle``        ``if` `(arr[i - 2] + arr[i - 1] > arr[i])``        ``{``            ``flag = 1;``            ``break``;``        ``}``    ``}` `    ``// If triplet found``    ``if` `(flag != 0)``    ``{``        ` `        ``// Print the triplet``        ``Console.Write(arr[i - 2] + ``" "` `+``                      ``arr[i - 1] + ``" "` `+``                      ``arr[i] );``    ``}` `    ``// Otherwise``    ``else``    ``{``        ``Console.Write(-1);``    ``}``}` `// Driver Code``public` `static` `void` `Main (``string` `[]args)``{``    ``int` `[]arr = { 4, 2, 10, 3, 5 };` `    ``int` `N = arr.Length;` `    ``findTriplet(arr, N);``}``}` `// This code is contributed by Ritik Bansal`
Output:
```3 4 5

```

Time Complexity: O(N*log(N))
Auxiliary Space: O(1)

Attention reader! Don’t stop learning now. Get hold of all the important mathematical concepts for competitive programming with the Essential Maths for CP Course at a student-friendly price. To complete your preparation from learning a language to DS Algo and many more,  please refer Complete Interview Preparation Course.

My Personal Notes arrow_drop_up