题目：

题解：

class Solution:
    def binaryTreePaths(self, root: TreeNode) -> List[str]:
        paths = list()
        if not root:
            return paths

        node_queue = collections.deque([root])
        path_queue = collections.deque([str(root.val)])

        while node_queue:
            node = node_queue.popleft()
            path = path_queue.popleft()

            if not node.left and not node.right:
                paths.append(path)
            else:
                if node.left:
                    node_queue.append(node.left)
                    path_queue.append(path + '->' + str(node.left.val))
                
                if node.right:
                    node_queue.append(node.right)
                    path_queue.append(path + '->' + str(node.right.val))
        return paths