Pair Cube Count Java

PROGRAM TO COUNT PAIRS (a, b) WHOSE SUM OF CUBES IS N (a^3+b^3 = N)

class Main

{

    // method to count the pairs satisfying

    // a ^ 3 + b ^ 3 = N

    static int countPairs(int N)

    {

        int count = 0;

       

        // Check for each number 1 to cbrt(N)

        for (int i = 1; i <= Math.cbrt(N); i++)

        {

            // Store cube of a number

            int cb = i*i*i;

       

            // Subtract the cube from given N

            int diff = N - cb;

       

            // Check if the difference is also

            // a perfect cube

            int cbrtDiff = (int) Math.cbrt(diff);

       

            // If yes, then increment count

            if (cbrtDiff*cbrtDiff*cbrtDiff == diff)

                count++;

        }

       

        // Return count

        return count;

    }

      

    // Driver method

    public static void main(String args[]) 

    {

        // Loop to Count no. of pairs satisfying

        // a ^ 3 + b ^ 3 = i for N = 1 to 10

        for (int i = 1; i<= 10; i++)

            System.out.println("For n = " + i + ", " +

                     + countPairs(i) + " pair exists");

    }

}




OUTPUT

For n= 1, 1 pair exists
For n= 2, 1 pair exists
For n= 3, 0 pair exists
For n= 4, 0 pair exists
For n= 5, 0 pair exists
For n= 6, 0 pair exists
For n= 7, 0 pair exists
For n= 8, 1 pair exists
For n= 9, 2 pair exists
For n= 10, 0 pair exists

CREDITS: https://www.geeksforgeeks.org/count-pairs-a-b-whose-sum-of-cubes-is-n-a3-b3-n/