题目：在二叉搜索树里找符合条件的节点值并求和

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.

我的答案

    public int rangeSumBST(TreeNode root, int L, int R) {
        if (root == null) {
            return 0;
        }
        int valToAdd = (root.val < L || root.val > R) ? 0 : root.val;
        return valToAdd + rangeSumBST(root.left, L, R) + rangeSumBST(root.right, L, R);
    }

我的分析

这道题很简单，本质上是二叉树的遍历，前中后序都可以