难度：中等

很简单，从第 0 步开始模拟即可，唯一sb的就是测试用例中如果（0，0）处不为0的话就直接false，而不是去找0在哪
我的代码：

class Solution:
    def checkValidGrid(self, grid: List[List[int]]) -> bool:
        nx, ny = 0, 0
        step = 0
        n = len(grid)

        if grid[0][0] != 0:
            return False

        def j(x, y):
            if x < 0 or x >= n or y < 0 or y >= n:
                return False
            if grid[x][y] == step:
                return True
            return False

        while step < len(grid) ** 2 - 1:
            step += 1
            if j(nx + 1, ny + 2):
                nx += 1
                ny += 2
                continue
            if j(nx + 2, ny + 1):
                nx += 2
                ny += 1
                continue
            if j(nx + 1, ny - 2):
                nx += 1
                ny -= 2
                continue
            if j(nx + 2, ny - 1):
                nx += 2
                ny -= 1
                continue
            if j(nx - 1, ny - 2):
                nx -= 1
                ny -= 2
                continue
            if j(nx - 2, ny - 1):
                nx -= 2
                ny -= 1
                continue
            if j(nx - 2, ny + 1):
                nx -= 2
                ny += 1
                continue
            if j(nx - 1, ny + 2):
                nx -= 1
                ny += 2
                continue
            return False
        
        return True

最好还是单独列出行动方式，而不是写多个if判断

directions = [
    [-2, 1],
    [-2, -1],
    [2, 1],
    [2, -1],
    [1, 2],
    [1, -2],
    [-1, 2],
    [-1, -2]
]
#或者这样
for j in ((-2,-1),(-2,1),(-1,2),(-1,-2),(1,2),(1,-2),(2,1),(2,-1)):