498 对角线遍历.md ​

class Solution:
  def findDiagonalOrder(self, mat: List[List[int]]) -> List[int]:
    m = len(mat) # y 方向
    n = len(mat[0]) # x 方向

    direction = 'up'
    i = 0 # y 方向
    j = 0 # x 方向

    answer = []

    while i < m or n < n:
      answer.append(mat[i][j])

      if i == m-1 and j == n -1:
        break
      # 向上到顶，换方向
      elif i == 0 and direction == 'up':
        direction = 'down'
        # 判断右上角处理
        if j == n -1:
          i += 1
        else:
          j += 1
      # 向上右边到顶换方向
      elif j == n -1 and direction == "up":
        i += 1
        direction = 'down'
      # 向下左边到顶
      elif j == 0 and direction == "down":
        direction = 'up'
        # 处理左下角
        if i == m -1:
          j += 1
        else:
          i += 1
      elif i == m -1 and direction == 'down':
        direction = 'up'
        j += 1
      elif direction == 'up':
        i -= 1
        j += 1
      elif direction == 'down':
        i += 1
        j -= 1

    return answer