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
题目含义：给定一棵二叉搜索树和最小最大边界L和R，修剪这棵树，使得其中的元素位于L和R之间。
1 public TreeNode trimBST(TreeNode root, int L, int R) { 2 if (root == null) return null; 3 4 if (root.val < L) return trimBST(root.right, L, R); 5 if (root.val > R) return trimBST(root.left, L, R); 6 7 root.left = trimBST(root.left, L, R); 8 root.right = trimBST(root.right, L, R); 9 10 return root; 11 }