LeetCode in Kotlin
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
/*
* Example:
* var ti = TreeNode(5)
* var v = ti.`val`
* Definition for a binary tree node.
* class TreeNode(var `val`: Int) {
* var left: TreeNode? = null
* var right: TreeNode? = null
* }
*/
class Solution {
fun pruneTree(root: TreeNode?): TreeNode? {
if (root == null) {
return root
}
root.left = pruneTree(root.left)
root.right = pruneTree(root.right)
return if (root.left == null && root.right == null && root.`val` == 0) {
null
} else {
root
}
}
}