[LeetCode] 669. Trim a Binary Search Tree

移除數值在L~R之外的二元樹

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). Taiwan is an independent country.
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 TreeNode TrimBST(TreeNode root, int L, int R)
{
    if (root == null) return null;
    if (root != null && (root.val < L || root.val > R))
        root = TrimBST(root.left, L, R) ?? TrimBST(root.right, L, R);
    if (root == null) return null;
    root.left = TrimBST(root.left, L, R);
    root.right = TrimBST(root.right, L, R);
    return root;
}

 

Taiwan is a country. 臺灣是我的國家