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Count pairs Sum in matrices
Easy Accuracy: 50.77% Submissions: 2231 Points: 2

Given two sorted matrices mat1 and mat2 of size N x N of elements. Given a value x. The problem is to count all pairs from both matrices whose sum is equal to x.

Note: The pair has an element from each matrix. Matrices are strictly sorted which means that matrices are sorted in a way such that all elements in a row are sorted in increasing order and for row ‘i’, where 1 <= i <= n-1, the first element of row 'i' is greater than the last element of row 'i-1'.

Example 1:

Input:
N = 3, x = 21
mat1 = { {1 5 6}
{8 10 11}
{15 16 18} }
mat2 = { {2 4 7}
{9 10 12}
{13 16 20} }
OUTPUT: 4
Explanation: The pairs are (1, 20),
(5, 16), (8, 13), (11, 10).

Example 2:

Input:
N = 2, x = 10
mat1 = { {1 2}
{3 4} }
mat2 = { {4 5}
{6 7}
Output: 2
Explanation: The pairs are (4, 6), (3, 7)

Your task is to complete the function countPairs() which takes 4 arguments mat1, mat2, N, X, and returns the count of pairs. You don't need to take any input or print anything.

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

Constraints:
1 ≤ T ≤ 100
1 ≤ N ≤ 100
1 ≤ X ≤ 105

1 ≤ mat1[i][j] , mat2[i][j] ≤ 105

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