zombie debug

题目：
Given a 2D grid, each cell is either a wall 2, a zombie 1 or people 0 (the number zero, one, two).Zombies can turn the nearest people(up/down/left/right) into zombies every day, but can not through wall. How long will it take to turn all people into zombies? Return -1 if can not turn all people into zombies.

Example

Given a matrix:
0 1 2 0 0
1 0 0 2 1
0 1 0 0 0
return 2

出现bug时应该，写case 来测试每个函数

class Solution:
    # @param {int[][]} grid  a 2D integer grid
    # @return {int} an integer
    def zombie(self, grid):
        # Write your code here
        n, m = len(grid), len(grid[0])
        queue = []

        for i in range(n):
            for j in range(m):
                if grid[i][j] == 1:
                    queue.append((i, j))
        p = []
        days = 0
        while queue:
            size = len(queue)
            for i in range(size):
                i, j = queue.pop(0)
                for x, y in self.getNeighbors(grid, i, j):
                    if grid[x][y] == 0:
                        p.append((x,y))
                        queue.append((x, y))
                        grid[x][y] = 1
            days += 1

        for i in range(n):
            for j in range(m):
                if grid[i][j] == 0:
                    return -1
        return days - 1  # 最后一天queue里只有zombie，把queue排空时并没有咬人，所以不算

    def getNeighbors(self, grid, i, j):
        dirs = [[1, 0], [-1, 0], [0, 1], [0, -1]]
        result = []
        for dx, dy in dirs:
            if self.inBound(grid, i + dx, j + dy):
                result.append((i + dx, j + dy))
        return result

    def inBound(self, grid, i, j):
        n, m = len(grid), len(grid[0])
        return i >= 0 and i < n and j >= 0 and j < m   # !!!! care j < m 蠢哭

m = [[0,1,2,0,0],
[1,0,0,2,1],
[0,1,0,0,0]]

res = Solution().zombie(m)
print(res) # 2