TrimBST669

[underwindfall]

• https://leetcode-cn.com/problems/trim-a-binary-search-tree/

• 思路

  • dfs recursive

• [x] 刷15mins

• [x] 刷5mins

   // time O(N)
    // espace O(N)
  public TreeNode trimBST(TreeNode root, int low, int high) {
        if (root == null) {
            return root;
        }
        if (root.val > high) {
            return trimBST(root.left, low, high);
        }
        if (root.val < low) {
            return trimBST(root.right, low, high);
        }
        root.left = trimBST(root.left, low, high);
        root.right = trimBST(root.right, low, high);
        return root;
    }