Triplet Sum in Array.cpp

/*
Triplet Sum in Array
====================

Given an array arr of size N and an integer K. Find if there's a triplet in the array which sums up to the given integer K.

Example 1:
Input:
N = 6, K = 13
arr[] = [1 4 45 6 10 8]
Output:
true
Explanation:
The triplet {1, 4, 8} in 
the array sums up to 13.

Example 2:
Input:
N = 5, K = 10
arr[] = [1 2 4 3 6]
Output:
true
Explanation:
The triplet {1, 3, 6} in 
the array sums up to 10.

Your Task:
You don't need to read input or print anything. Your task is to complete the function find3Numbers() which takes the array arr[], the size of the array (N) and the sum (X) as inputs and returns True if there exists a triplet in the array arr[] which sums up to X and False otherwise.

Expected Time Complexity: O(N2)
Expected Auxiliary Space: O(1)

Constraints:
1 ≤ N ≤ 103
1 ≤ A[i] ≤ 105
*/

// function to find the triplet which sum to x
// arr[] : The input Array
// N : Size of the Array
// X : Sum which you need to search for

bool find3Numbers(int arr[], int N, int X)
{
  sort(arr, arr + N);
  for (int i = 0; i < N; ++i)
  {
    int j = i + 1, k = N - 1;
    while (j < k)
    {
      if (arr[i] + arr[j] + arr[k] == X)
        return true;
      else if (arr[i] + arr[j] + arr[k] > X)
        k--;
      else
        j++;
    }
  }
  return false;
}