题目:
题解:
python
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