Description
Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the result should return the new root of the trimmed binary search tree.
Example 1:
Input:
tree
L = 1
R = 2
Output:
trimed
Example 2:
Input:
tree
L = 1
R = 3
Output:
trimed
Solution
DFS
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public TreeNode trimBST(TreeNode root, int L, int R) {
if (root == null) {
return null;
}
if (root.val < L) {
return trimBST(root.right, L, R);
} else if (root.val > R) {
return trimBST(root.left, L, R);
} else {
root.left = trimBST(root.left, L, R);
root.right = trimBST(root.right, L, R);
return root;
}
}
}
