LeetCode之Range Sum of BST（Kotlin）

問題： 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.
複製代碼

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方法： 對二叉搜索樹進行遞歸遍歷，判斷節點的值是否在值範圍，而後求和便可，具體實現看代碼。

具體實現：

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>) {

}
複製代碼

有問題隨時溝通

具體代碼實現能夠參考Github