Count pairs Sum in matrices Python

PROGRAM TO COUNT PAIRS FROM TWO SORTED MATRICES WITH GIVEN SUM

SIZE = 10

  

# function to count pairs from two sorted matrices

# whose sum is equal to a given value x

def countPairs(mat1, mat2, n, x):

      

    # 'r1' and 'c1' for pointing current element

    # of mat1[][]

    # 'r2' and 'c2' for pointing current element

    # of mat2[][]

    r1 = 0

    c1 = 0

    r2 = n - 1

    c2 = n - 1

      

    # while there are more elements

    # in both the matrices

    count = 0

    while ((r1 < n) and (r2 >= -1)):

          

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

          

        # if true

        if (val == x):

              

            # increment 'count'

            count += 1

              

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

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

            c1 += 1

            c2 -= 1

              

        # if true, move mat1[][] column 'c1' to right

        elif (val < x):

            c1 += 1

          

        # else move mat2[][] column 'c2' to left

        else:

            c2 -= 1

              

        # if 'c1' crosses right boundary

        if (c1 == n):

              

            # reset 'c1'

            c1 = 0

              

            # increment row 'r1'

            r1 += 1

              

        # if 'c2' crosses left boundary

        if (c2 == -1):

              

            # reset 'c2'

            c2 = n - 1

              

            # decrement row 'r2'

            r2 -= 1

              

    # required count of pairs

    return count

  

# Driver program to test above

mat1 = [ [1, 5, 6] ,[8, 10, 11 ],[15, 16, 18 ]]

  

mat2 = [[2, 4, 7],[ 9, 10, 12],[13, 16, 20]]

  

n = 3

x = 21

  

print("Count =",countPairs(mat1, mat2, n, x))

OUTPUT

Count = 4

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