Populate the ndarrays in `payoff_arrays` with the payoff values of
    the SGC game.

    Parameters
    ----------
    payoff_arrays : tuple(ndarray(float, ndim=2))
        Tuple of 2 ndarrays of shape (4*k-1, 4*k-1). Modified in place.

def _populate_sgc_payoff_arrays(payoff_arrays):
    """
    Populate the ndarrays in `payoff_arrays` with the payoff values of
    the SGC game.

    Parameters
    ----------
    payoff_arrays : tuple(ndarray(float, ndim=2))
        Tuple of 2 ndarrays of shape (4*k-1, 4*k-1). Modified in place.

    """
    n = payoff_arrays[0].shape[0]  # 4*k-1
    m = (n+1)//2 - 1  # 2*k-1
    for payoff_array in payoff_arrays:
        for i in range(m):
            for j in range(m):
                payoff_array[i, j] = 0.75
            for j in range(m, n):
                payoff_array[i, j] = 0.5
        for i in range(m, n):
            for j in range(n):
                payoff_array[i, j] = 0

        payoff_array[0, m-1] = 1
        payoff_array[0, 1] = 0.5
        for i in range(1, m-1):
            payoff_array[i, i-1] = 1
            payoff_array[i, i+1] = 0.5
        payoff_array[m-1, m-2] = 1
        payoff_array[m-1, 0] = 0.5

    k = (m+1)//2
    for h in range(k):
        i, j = m + 2*h, m + 2*h
        payoff_arrays[0][i, j] = 0.75
        payoff_arrays[0][i+1, j+1] = 0.75
        payoff_arrays[1][j, i+1] = 0.75
        payoff_arrays[1][j+1, i] = 0.75