题解 | 求二叉树的层序遍历

# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 
# @param root TreeNode类 
# @return int整型二维数组
#
class Solution:
    def levelOrder(self , root: TreeNode) -> List[List[int]]:
        # write code here
        if not root:
            return []
        s, ans = [root], []
        while s:
            n, cur = len(s), []
            for _ in range(n):
                p = s.pop(0)
                cur.append(p.val)
                if p.left:
                    s.append(p.left)
                if p.right:
                    s.append(p.right)
            ans.append(cur)
        return ans