# [Solved] Given the root of a binary tree, return the same tree where every subtree (of the given tree) not containing a 1 has been removed. A subtree of a node node is node plus every node that is a descendant of node.

## Question

Given the `root` of a binary tree, return the same tree where every subtree (of the given tree) not containing a `1` has been removed.

A subtree of a node `node` is `node` plus every node that is a descendant of `node`.

Example 1:

```Input: root = [1,null,0,0,1]
Output: [1,null,0,null,1]
Explanation:
Only the red nodes satisfy the property "every subtree not containing a 1".
The diagram on the right represents the answer.
```

Example 2:

```Input: root = [1,0,1,0,0,0,1]
Output: [1,null,1,null,1]
```

Example 3:

```Input: root = [1,1,0,1,1,0,1,0]
Output: [1,1,0,1,1,null,1]
```

Constraints:

• The number of nodes in the tree is in the range `[1, 200]`.
• `Node.val` is either `0` or `1`.

## Python Solution

```# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
def prune(root,parent):
if root==None:return

prune(root.left,root)
prune(root.right,root)
if root.left==None and root.right==None and root.val==0:
if parent.left == root:
parent.left = None
else:
parent.right = None

class Solution:
def pruneTree(self, root: TreeNode) -> TreeNode:
prune(root,None)
return root```