LCOF 47. Maximum Value of Presents

class Solution:
  def maxValue(self, grid: List[List[int]]) -> int:
    m = len(grid)
    n = len(grid[0])
    dp = [[0] * n for _ in range(m)]
    dp[0][0] = grid[0][0]
    for i in range(m):
      for j in range(n):
        dp[i][j] = grid[i][j] + max(i and dp[i-1][j], j and dp[i][j-1])
    return dp[-1][-1]