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LeetCode.938.Range Sum of BST 二叉搜索树BST的范围和

题目描述

938 Range Sum of BST
https://leetcode-cn.com/problems/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:

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

Example 2:

  1. Input: root = [10,5,15,3,7,13,18,1,null,6], L = 6, R = 10
  2. 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.


解题过程

递归深度优先搜索 + 利用BST的性质剪枝
时间复杂度 O(n),空间复杂度 O(n)

  1. private static class SolutionV2020 {
  2. public int rangeSumBST(TreeNode root, int L, int R) {
  3. return dfs(root, L, R);
  4. }
  5. // 递归遍历二叉树,返回root中在[L,R]之间的结点和
  6. private int dfs(TreeNode root, int L, int R) {
  7. if (null == root) {
  8. return 0;
  9. }
  10. // 剪枝,剪掉根和右子树
  11. if (root.val > R) {
  12. return dfs(root.left, L, R);
  13. }
  14. // 剪枝,剪掉根和左子树
  15. if (root.val < L) {
  16. return dfs(root.right, L, R);
  17. }
  18. // 根在[L,R]之间
  19. return root.val + dfs(root.left, L, R) + dfs(root.right, L, R);
  20. }
  21. }

GitHub代码

algorithms/leetcode/leetcode/_938_RangeSumOfBST.java
https://github.com/masikkk/algorithms/blob/master/leetcode/leetcode/_938_RangeSumOfBST.java


上一篇 LeetCode.965.Univalued Binary Tree 单值二叉树

下一篇 LeetCode.897.Increasing Order Search Tree BST转升序单边树

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