[leetcode] 938. Range Sum of BST @ python

最新推荐文章于 2024-06-06 19:39:31 发布

原创最新推荐文章于 2024-06-06 19:39:31 发布 · 336 阅读

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博客围绕二叉搜索树展开，给出题目：求值在L和R之间（包含）的所有节点值之和，还给出示例及注意事项。解法是通过中序遍历，将符合条件的节点放入列表，最后返回列表的和。

原题

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.

解法

中序遍历, 将符合条件的节点放入列表中, 最后返回列表的和.

代码

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def rangeSumBST(self, root, L, R):
        """
        :type root: TreeNode
        :type L: int
        :type R: int
        :rtype: int
        """
        l = []
        def inOrder(root):
            if not root:
                return
            inOrder(root.left)
            if L <= root.val <= R:
                l.append(root.val)
            inOrder(root.right)
            
        inOrder(root)
        return sum(l)