938. Range Sum of BST

catepk·2021년 8월 22일
0

LeetCode

목록 보기
52/88
post-thumbnail

938. Range Sum of BST

문제

Given the root node of a binary search tree and two integers low and high, return the sum of values of all nodes with a value in the inclusive range [low, high].

Example 1:

Input: root = [10,5,15,3,7,null,18], low = 7, high = 15
Output: 32
Explanation: Nodes 7, 10, and 15 are in the range [7, 15]. 7 + 10 + 15 = 32.

Example 2:

Input: root = [10,5,15,3,7,13,18,1,null,6], low = 6, high = 10
Output: 23
Explanation: Nodes 6, 7, and 10 are in the range [6, 10]. 6 + 7 + 10 = 23.

Constraints:

The number of nodes in the tree is in the range [1, 2 * 10^4].
1 <= Node.val <= 10^5
1 <= low <= high <= 10^5
All Node.val are unique.

풀이

-----Brute Force-----

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
        if not root:
            return 0
        return (root.val if low <= root.val <= high else 0) + self.rangeSumBST(root.left, low, high) + self.rangeSumBST(root.right, low, high)

-----DFS-----

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
        def dfs(node: TreeNode):
            if not node:
                return 0
            if node.val < low:
                return dfs(node.right)
            elif node.val > high:
                return dfs(node.left)
            return node.val + dfs(node.left) + dfs(node.right)
        return dfs(root)

-----DFS-----

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
        stack = [root]
        sums = 0
        while stack:
            node = stack.pop()
            if node:
                if node.val > low:
                    stack.append(node.left)
                if node.val < high:
                    stack.append(node.right)
                if low <= node.val <= high:
                    sums += node.val
        return sums

-----BFS-----

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def rangeSumBST(self, root: Optional[TreeNode], low: int, high: int) -> int:
        stack = [root]
        sums = 0
        while stack:
            node = stack.pop(0)
            if node:
                if node.val > low:
                    stack.append(node.left)
                if node.val < high:
                    stack.append(node.right)
                if low <= node.val <= high:
                    sums += node.val
        return sums
profile
hello

0개의 댓글