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.
题目地址
这道题考察的是简单的二叉树遍历，你可以使用三种遍历中的任何一种（先序、中序、后序），下面我使用先序遍历来解题：
Java代码
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
private int result=0;
public int rangeSumBST(TreeNode root, int L, int R) {
if(root==null)
return result;
if(root.val>=L && root.val<=R){
result += root.val;
}
rangeSumBST(root.left, L, R);
rangeSumBST(root.right, L, R);
return result;
}
}