LeetCode938_二叉搜尋樹的範圍和

1. 題目

2. 題解

# 938
from collections import deque


class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

class Solution:
    # 方法1： 遞歸法
    def rangeSumBST(self, root: TreeNode, low: int, high: int) -> int:
        if root is None:
            return 0

        leftSum = self.rangeSumBST(root.left, low, high)
        rightSum = self.rangeSumBST(root.right, low, high)
        result = leftSum + rightSum
        if low <= root.val <= high:
            result += root.val
        return result

    # 方法2： BFS 寬度優先搜尋
    def rangeSumBST_2(self, root: TreeNode, low: int, high: int) -> int:
        result = 0
        q = deque()
        q.append(root)
        while len(q) > 0:
            size = len(q)
            while size > 0:
                cur = q.popleft()
                if low <= cur.val <= high:
                    result += cur.val
                if cur.left is not None:
                    q.append(cur.left)

                if cur.right is not None:
                    q.append(cur.right)

                size = size - 1

        return