I don't agree with you.

Modern C++ is not just C with classes.
Completely different constructions are used to solve problems.

Why is a function signature in с-style given for C++ kata?

void check_is_contained(int **mat1, const int mat2[3][3],const int nrows, const int ncols, int &row, int &col)

I propose changing to c++ style

std::pair<int, int> check_is_contained(std::vector<std::vector<int>> mat1, std::vector<std::vector<int>> mat2)
{
  // solution
  return { row, col }; // or tuple
}

great

I have some problems with test case - "minDiff on random generated piles should be ok"
Input: List(979860, 858272, 854452, 698901, 687688, 684485, 493090, 306875, 292611, 290339, 266237, 82990)

Output:

Test Failed
30064 was not equal to 2520

I think the problem is in the test because my result is correct

My result: first stone = 3232868, second stone = 3262932, and min diff number = 30064

I don't think so. The length of the lines is the same.

 ****************** Random Tests **** orderWeight
136
136

I think the problem is in the test. Most likely my result is compared with an incorrect value. In the fixed test everything is correct.

I have the same problem