python - 围绕矩阵周长移动值 - Python/NumPy

Question

横向值必须沿周长移动。

例如一步扭转:

1 2 3     4 1 2
4 5 6 ==> 7 5 3
7 8 9     8 9 6

Answer 1

这是2D数组的一种方法 -

def move_perimeter(a, n, direction='clockwise'):
    # a : input array
    # n : number of elements to be moved
    # direction : 'clockwise' or 'counterclockwise'

    # Dictionary to map for number of elements rolling later
    dirn_map = {'clockwise':n,'counterclockwise':-n}

    # Store size
    m,n = a.shape
    r0 = np.arange(m-1)
    r1 = np.arange(n-1)

    # Get Top, Right, Bottom and Left side linear indices. Store those.
    T = r1
    R = n-1+r0*n
    B = a.size-r1-1
    L = n+r0[::-1]*n
    idx = np.r_[T,R,B,L]

    # Make a copy of input array
    out = a.copy()

    # Linearly index into output array with those original indices
    # and extract rolled values from input array.
    out.ravel()[idx] = a.ravel()[np.roll(idx, dirn_map[direction])]
    return out

示例运行 -

In [233]: a
Out[233]: 
array([[83, 13, 27, 13],
       [90, 78, 57, 68],
       [66, 47, 44, 53],
       [13, 98, 95, 46],
       [29, 87, 80, 92],
       [91, 19, 86, 26],
       [31, 27, 75, 72]])

In [234]: move_perimeter(a, n=1, direction='clockwise')
Out[234]: 
array([[90, 83, 13, 27],
       [66, 78, 57, 13],
       [13, 47, 44, 68],
       [29, 98, 95, 53],
       [91, 87, 80, 46],
       [31, 19, 86, 92],
       [27, 75, 72, 26]])

In [235]: move_perimeter(a, n=2, direction='counterclockwise')
Out[235]: 
array([[27, 13, 68, 53],
       [13, 78, 57, 46],
       [83, 47, 44, 92],
       [90, 98, 95, 26],
       [66, 87, 80, 72],
       [13, 19, 86, 75],
       [29, 91, 31, 27]])