面試題32：從上到下打印二叉樹

# 面試題32：從上到下打印二叉樹

# 定義二叉樹節點
class BinaryTreeNode:
    def __init__(self, val):
        self.val = val
        self.left = None
        self.right = None
class Solution:
    # 從上到下按層打印
    def Print_Up_Down(self, tree):
        # 構造隊列
        queue = []
        # 構造打印結果列表
        result = []
        if not tree:
            return False
        queue.append(tree)
        while queue:
            tree = queue[0]
            if tree.left:
                queue.append(tree.left)
            if tree.right:
                queue.append(tree.right)
            queue.pop(0)
            # 打印結果
            result.append(tree.val)
        return result

if __name__=="__main__":
    # 構造二叉樹
    tree = BinaryTreeNode(8)
    tree.left = BinaryTreeNode(6)
    tree.right = BinaryTreeNode(10)
    tree.left.left = BinaryTreeNode(5)
    tree.left.right = BinaryTreeNode(7)
    tree.right.left = BinaryTreeNode(9)
    tree.right.right = BinaryTreeNode(11)

    solution = Solution()
    print(solution.Print_Up_Down(tree))