Java
/**
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:
1
/ \
0 2
L = 1
R = 2
Output:
1
\
2
Example 2:
Input:
3
/ \
0 4
\
2
/
1
L = 1
R = 3
Output:
3
/
2
/
1
*/
public class Trim_a_Binary_Search_Tree {
/*
Input:
1
/ \
0 2
L = 0
R = 0
Output:
0
*/
/**
* 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) {
// basic rule: if root is deleted, the move right to be new root
if (root == null) {
return null;
}
if (root.val < L) {
// then all its left children are less than L, only return right child
root = trimBST(root.right, L, R);
}
else if (root.val > R) {
// then all its right children bigger than R, and disgarded
root = trimBST(root.left, L, R);
}
else {
root.left = trimBST(root.left, L, R);
root.right = trimBST(root.right, L, R);
}
return root;
}
}
}Java
/**
* 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) {
while (root != null && root.val < L)
root = root.right;
if (root == null)
return null;
TreeNode parentLeft = root, childLeft = root.left;
while (childLeft != null) {
if (childLeft.val < L) {
parentLeft.left = childLeft.right;
childLeft = childLeft.right;
} else {
parentLeft = childLeft;
childLeft = childLeft.left;
}
}
while (root != null && root.val > R)
root = root.left;
if (root == null)
return null;
TreeNode parentRight = root, childRight = root.right;
while (childRight != null) {
if (childRight.val > R) {
parentRight.right = childRight.left;
childRight = childRight.left;
} else {
parentRight = childRight;
childRight = childRight.right;
}
}
return root;
}
}