题目：

题解：

class Solution:

    DIRS = [(-1, 0), (1, 0), (0, -1), (0, 1)]

    def longestIncreasingPath(self, matrix: List[List[int]]) -> int:
        if not matrix:
            return 0
        
        rows, columns = len(matrix), len(matrix[0])
        outdegrees = [[0] * columns for _ in range(rows)]
        queue = collections.deque()
        for i in range(rows):
            for j in range(columns):
                for dx, dy in Solution.DIRS:
                    newRow, newColumn = i + dx, j + dy
                    if 0 <= newRow < rows and 0 <= newColumn < columns and matrix[newRow][newColumn] > matrix[i][j]:
                        outdegrees[i][j] += 1
                if outdegrees[i][j] == 0:
                    queue.append((i, j))

        ans = 0
        while queue:
            ans += 1
            size = len(queue)
            for _ in range(size):
                row, column = queue.popleft()
                for dx, dy in Solution.DIRS:
                    newRow, newColumn = row + dx, column + dy
                    if 0 <= newRow < rows and 0 <= newColumn < columns and matrix[newRow][newColumn] < matrix[row][column]:
                        outdegrees[newRow][newColumn] -= 1
                        if outdegrees[newRow][newColumn] == 0:
                            queue.append((newRow, newColumn))
        
        return ans