Java Program to Count triplets with sum smaller than a given value

// A Simple Java program to count triplets with sum smaller
// than a given value

class Test
{
    static int arr[] = new int[]{5, 1, 3, 4, 7};
    
    static int countTriplets(int n, int sum)
    {
        // Initialize result
        int ans = 0;
     
        // Fix the first element as A[i]
        for (int i = 0; i < n-2; i++)
        {
           // Fix the second element as A[j]
           for (int j = i+1; j < n-1; j++)
           {
               // Now look for the third number
               for (int k = j+1; k < n; k++)
                   if (arr[i] + arr[j] + arr[k] < sum)
                       ans++;
           }
        }
     
        return ans;
    }
    
    // Driver method to test the above function
    public static void main(String[] args) 
    {
        int sum = 12; 
        System.out.println(countTriplets(arr.length, sum));
    }
}

// A Simple Java program to count triplets with sum smaller
// than a given value

import java.util.Arrays;

class Test
{
    static int arr[] = new int[]{5, 1, 3, 4, 7};
    
    static int countTriplets(int n, int sum)
    {
        // Sort input array
        Arrays.sort(arr);
     
        // Initialize result
        int ans = 0;
     
        // Every iteration of loop counts triplet with
        // first element as arr[i].
        for (int i = 0; i < n - 2; i++)
        {
            // Initialize other two elements as corner elements
            // of subarray arr[j+1..k]
            int j = i + 1, k = n - 1;
     
            // Use Meet in the Middle concept
            while (j < k)
            {
                // If sum of current triplet is more or equal,
                // move right corner to look for smaller values
                if (arr[i] + arr[j] + arr[k] >= sum)
                    k--;
     
                // Else move left corner
                else
                {
                    // This is important. For current i and j, there
                    // can be total k-j third elements.
                    ans += (k - j);
                    j++;
                }
            }
        }
        return ans;
    }
    
    // Driver method to test the above function
    public static void main(String[] args) 
    {
        int sum = 12; 
        System.out.println(countTriplets(arr.length, sum));
    }
}