LeetCode-in-Java
814. Binary Tree Pruning
Medium
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.valis either0or1.
Solution
import com_github_leetcode.TreeNode;
/*
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
public class Solution {
public TreeNode pruneTree(TreeNode root) {
if (root == null) {
return root;
}
root.left = pruneTree(root.left);
root.right = pruneTree(root.right);
if (root.left == null && root.right == null && root.val == 0) {
return null;
}
return root;
}
}