---
# System prepended metadata

title: 814_Binary_Tree_Pruning
tags: [leetcode]

---

# 814_Binary_Tree_Pruning
###### tags: `leetcode`
## Problem Statement
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

## Solution
- It should be done by iteratively looking for the possible one to delete
```cpp=
if (root->left!= NULL)
    root->left= pruneTree(root->left);
if (root->right!= NULL)
    root->right= pruneTree(root->right);
```
- Begin with the last leaf node, delete it if it is 0.
```cpp=
if (root->right== NULL&& root->left== NULL)
{
    if (root->val)
        return root;
    else
        return NULL;
}
```