LeetCode之Range Sum of BST（Kotlin）

问题： 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.
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方法： 对二叉搜索树进行递归遍历，判断节点的值是否在值范围，而后求和便可，具体实现看代码。

具体实现：

class RangeSumOfBST {
    // Definition for a binary tree node.
    class TreeNode(var `val`: Int = 0) {
        var left: TreeNode? = null
        var right: TreeNode? = null
    }

    fun rangeSumBST(root: TreeNode?, L: Int, R: Int): Int {
        if (root == null) {
            return 0
        }
        if (root.`val` in L..R) {
            return root.`val` + rangeSumBST(root.left, L, R) + rangeSumBST(root.right, L, R)
        } else {
            return rangeSumBST(root.left, L, R) + rangeSumBST(root.right, L, R)
        }
    }
}

fun main(args: Array<String>) {

}
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有问题随时沟通

具体代码实现能够参考Github