Count pairs Sum in matrices Java

PROGRAM TO COUNT PAIRS FROM TWO SORTED MATRICES WITH GIVEN SUM

import java.io.*;

  

class MAIN 

{

    int SIZE = 10;

      

    // function to count pairs from 

    // two sorted matrices whose sum 

    // is equal to a given value x

    static int countPairs(int mat1[][], int mat2[][],

                                        int n, int x)

    {

        // 'r1' and 'c1' for pointing current 

        // element of mat1[][]

        // 'r2' and 'c2' for pointing current 

        // element of mat2[][]

        int r1 = 0, c1 = 0;

        int r2 = n - 1, c2 = n - 1;

      

        // while there are more elements

        // in both the matrices

        int count = 0;

        while ((r1 < n) && (r2 >= -1)) 

        {

            int val = mat1[r1][c1] + mat2[r2][c2];

      

            // if true

            if (val == x) {

      

                // increment 'count'

                count++;

      

                // move mat1[][] column 'c1' to right

                // move mat2[][] column 'c2' to left

                c1++;

                c2--;

            }

      

            // if true, move mat1[][] 

            // column 'c1' to right

            else if (val < x)

                c1++;

      

            // else move mat2[][] column

            // 'c2' to left

            else

                c2--;

      

            // if 'c1' crosses right boundary

            if (c1 == n) {

      

                // reset 'c1'

                c1 = 0;

      

                // increment row 'r1'

                r1++;

            }

      

            // if 'c2' crosses left boundary

            if (c2 == -1) {

      

                // reset 'c2'

                c2 = n - 1;

      

                // decrement row 'r2'

                r2--;

            }

        }

      

        // required count of pairs

        return count;

    }

      

    // Driver code 

    public static void main (String[] args) 

    {

        int mat1[][] = { { 1, 5, 6 },

                         { 8, 10, 11 },

                         { 15, 16, 18 } };

  

        int mat2[][] = { { 2, 4, 7 },

                         { 9, 10, 12 },

                         { 13, 16, 20 } };

      

        int n = 3;

        int x = 21;

      

        System.out.println ( "Count = " + 

                            countPairs(mat1, mat2, n, x));

              

    }

}







OUTPUT

Count = 4

CREDITS: https://www.geeksforgeeks.org/count-pairs-two-sorted-matrices-given-sum/