算法题目-7周-Range Sum of BST

1、Range Sum of BST

Given the root node of a binary search tree, return the sum of values of all nodes with value between L and R (inclusive).

The binary search tree is guaranteed to have unique values.

Example 1:

Input: root = [10,5,15,3,7,null,18], L = 7, R = 15
Output: 32

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
Output: 23

Note:

The number of nodes in the tree is at most 10000.
The final answer is guaranteed to be less than 2^31.

Solve：

public int rangeSumBST(TreeNode root, int L, int R) {
           if(root==null){
               return 0;
           }
           int sum = 0;
           if(L<=root.val&&root.val<=R){
               sum = root.val;
           }
           if(L

Runtime: 0 ms, faster than 100.00% of Java online submissions for Range Sum of BST.
Memory Usage: 43.2 MB, less than 98.97% of Java online submissions for Range Sum of BST.