如何更改最近的邻居的功能以对角线不起作用

Question

我已经工作最近的邻居功能，但是我不知道如何使其仅在水平和垂直上工作，现在它在各个方向上工作。下面的代码：

nnlst = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
MAP_WIDTH = 3
MAP_HEIGHT = 3

def nearest_neighbors(map_x, map_y):
    coordinates_list = []
    for x_ in range(max(0, map_x - 1), min(MAP_WIDTH, map_x + 2)):
        for y_ in range(max(0, map_y - 1), min(MAP_HEIGHT, map_y + 2)):
            # we are ignoring result when x_ and y_ equals variable we ask for
            if (map_x, map_y) == (x_, y_):
                continue
            coordinates_list.append([x_, y_])
    return coordinates_list
print "function result"
print "nearest neighbors of", nnlst[0][1]
nearest_neighbor_coordinates_list = nearest_neighbors(0, 1)
for coordinates in nearest_neighbor_coordinates_list:
    print coordinates, "=", nnlst[coordinates[0]][coordinates[1]]

正如您现在可以看到的那样，它在各个方向上起作用。

Answer 1

您需要添加更多条件，以防止对角线包含：

def nearest_neighbors(map_x, map_y):
    coordinates_list = []
    for x_ in range(max(0, map_x - 1), min(MAP_WIDTH, map_x + 2)):
        for y_ in range(max(0, map_y - 1), min(MAP_HEIGHT, map_y + 2)):
            # we are ignoring result when x_ and y_ equals variable we ask for, also the diagonal neigbors that differ in both x & y coordinates
            if (map_x, map_y) == (x_, y_) or (map_x != x_ and map_y != y_):
                continue
            coordinates_list.append([x_, y_])
    return coordinates_list

获得所需的结果：

function result
nearest neighbors of 2
[0, 0] = 1
[0, 2] = 3
[1, 1] = 5

Answer 2

另外，您可以明确列出所有"可允许"位移：

for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
    x_ = min(MAP_WIDTH, max(0, map_x + dx))
    y_ = min(MAP_HEIGHT, max(0, map_y + dy))
    if (map_x, map_y) == (x_, y_):
        continue
    ...

Answer 3

对于诸如少数可能性之类的问题，我只会将它们全部拼写出来，并预先计算每个位置的功能结果。这样，就可以消除该功能，并且问题降低为进行简单的表查找操作。

这是我的意思：

nnlist = [[1, 2, 3],
          [4, 5, 6],
          [7, 8, 9]]
MAP_WIDTH = len(nnlist[0])
MAP_HEIGHT = len(nnlist)
nearest_neighbors = {}  # is now a dictionary
for x in range(MAP_WIDTH):
    for y in range(MAP_HEIGHT):
        neighbors = [[nx, ny] for nx, ny in [(x-1, y), (x+1, y), (x, y-1), (x, y+1)]
                                  if -1 < nx < MAP_WIDTH and -1 < ny < MAP_HEIGHT]
        nearest_neighbors[(x, y)] = neighbors
print "look-up result"
print "nearest neighbors of", nnlist[0][1]
nearest_neighbor_coordinates_list = nearest_neighbors[(0, 1)]
for coordinates in nearest_neighbor_coordinates_list:
    print coordinates, "=", nnlist[coordinates[0]][coordinates[1]]