二叉树示意图

tree_0.svg

队列实现

  1. def stack_print(root):
  2.     node = root
  3.     storage = [node]
  4.     result = []
  6.     while storage:
  7.         count = len(storage)
  8.         line = []
  9.         for i in range(count):
  10.             node = storage.pop(0)
  11.             line.append(node.val)
  13.             if node.left:
  14.                 storage.append(node.left)
  15.             if node.right:
  16.                 storage.append(node.right)
  17.         result.append(line)
  19.     return result