leetcode199

class Solution:
    def __init__(self):
        self.list = []
        self.result = []
        
    def levelOrder(self,level):
        count = len(level)
        while count > 0:
            root = level.pop(0)
            self.list.append(root.val)
            if root.left != None:
                level.append(root.left)
            if root.right != None:
                level.append(root.right)
            count -= 1
        if len(self.list) > 0:
            self.result.append(self.list[:])
            self.list = []
        if len(level) > 0:
            self.levelOrder(level)
            
    def rightSideView(self, root: TreeNode) -> List[int]:
        if root == None:
            return self.list
        else:
            level = []
            level.append(root)
            self.levelOrder(level)
            res = []
            for li in self.result:
                res.append(li[-1])
            return res

二叉树层次遍历，最后返回每一层的最后一个节点组成的集合。