5 posts tagged with "Tree"

from typing import Optional


# 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 Solution1:
    def largestValues(self, root: Optional[TreeNode]) -> list[int]:
        result, nodes = [], [x for x in [root] if x]
        while nodes:
            result.append(max(x.val for x in nodes))
            _next = []
            _next.extend([x.left for x in nodes if x.left])
            _next.extend([x.right for x in nodes if x.right])
            nodes = _next
        return result


class Solution:
    # https://leetcode.com/problems/find-largest-value-in-each-tree-row/solutions/99000/python-bfs/
    def largestValues(self, root: Optional[TreeNode]) -> list[int]:
        result, nodes = [], [root]
        while any(nodes):
            result.append(max(x.val for x in nodes))
            nodes = [x for n in nodes for x in [n.left, n.right] if x]
        return result

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


class Solution:
    def lowestCommonAncestor(self, root, p, q):
        if root.val > max(p.val, q.val):
            return self.lowestCommonAncestor(root.left, p, q)
        if root.val < min(p.val, q.val):
            return self.lowestCommonAncestor(root.right, p, q)
        return root

# 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 isValidBST(self, root, lo=float('-inf'), hi=float('inf')) -> bool:
        '''
        [5,4,6,null,null,3,7] => false
        '''
        return (not root) or all(
            [
                lo < root.val < hi,
                self.isValidBST(root.left, lo, root.val),
                self.isValidBST(root.right, root.val, hi),
            ]
        )

from functools import reduce


# 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 levelOrder(self, root) -> list[list[int]]:
        result, q = [], [root]
        while True:
            q = [x for x in q if x]
            v = [x.val for x in q]
            if not v:
                break
            result.append(v)
            q = reduce(lambda a, b: a + [b.left, b.right], q, [])
        return result

class Node:
    def __init__(self, val=None, children=None):
        self.val = val
        self.children = children


class Solution:
    def preorder(self, root):
        return (
            (root.val,) + sum((self.preorder(x) for x in root.children), ())
            if root
            else ()
        )