LeetCode题解(0919)：设计完全二叉树插入器(Python)

题目：​​原题链接​​（中等）

标签：树、二叉树、广度优先搜索、设计

解法一：

class CBTInserter:

    def __init__(self, root: TreeNode):
        self.root = root
        self.queue = collections.deque([root])
        while True:
            if self.queue[0].left:
                self.queue.append(self.queue[0].left)
            else:
                break
            if self.queue[0].right:
                self.queue.append(self.queue[0].right)
                self.queue.popleft()
            else:
                break

    def insert(self, v: int) -> int:
        if not self.queue[0].left:
            self.queue[0].left = TreeNode(v)
            self.queue.append(self.queue[0].left)
            return self.queue[0].val
        else:
            self.queue[0].right = TreeNode(v)
            self.queue.append(self.queue[0].right)
            return self.queue.popleft().val

    def get_root(self) -> TreeNode:
        return self.root

解法二（不再从列表中删除结点）：

class CBTInserter:

    def __init__(self, root: TreeNode):
        self.queue = [root]
        for node in self.queue:
            if node.left:
                self.queue.append(node.left)
            else:
                break
            if node.right:
                self.queue.append(node.right)
            else:
                break

    def insert(self, v: int) -> int:
        self.queue.append(TreeNode(v))
        idx, sub = divmod(len(self.queue), 2)
        if sub == 0:
            self.queue[idx - 1].left = self.queue[-1]
        else:
            self.queue[idx - 1].right = self.queue[-1]
        return self.queue[idx - 1].val

    def get_root(self) -> TreeNode:
        return self.queue[0]