用循环体输入生成二叉树，输入quit停止生成二叉树

好的，这里给出一个用循环体输入生成二叉树的示例代码：

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def build_tree():
    # 根节点
    root_val = input("Enter the root value (quit to stop): ")
    if root_val.lower() == "quit":
        return None
    root = TreeNode(int(root_val))

    # 循环体输入左右子树
    queue = [root]
    while queue:
        node = queue.pop(0)
        # 输入左子树
        left_val = input(f"Enter the left child of {node.val} (quit to stop): ")
        if left_val.lower() != "quit":
            left = TreeNode(int(left_val))
            node.left = left
            queue.append(left)
        # 输入右子树
        right_val = input(f"Enter the right child of {node.val} (quit to stop): ")
        if right_val.lower() != "quit":
            right = TreeNode(int(right_val))
            node.right = right
            queue.append(right)

    return root

使用方法：

root = build_tree()

示例输入：

Enter the root value (quit to stop): 1
Enter the left child of 1 (quit to stop): 2
Enter the right child of 1 (quit to stop): 3
Enter the left child of 2 (quit to stop): 4
Enter the right child of 2 (quit to stop): quit
Enter the left child of 3 (quit to stop): quit
Enter the right child of 3 (quit to stop): 5
Enter the left child of 4 (quit to stop): quit
Enter the right child of 4 (quit to stop): quit
Enter the left child of 5 (quit to stop): quit
Enter the right child of 5 (quit to stop): quit

生成的二叉树：

     1
   /   \
  2     3
 /     /
4     5