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103. Binary Tree Zigzag Level Order Traversal # 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 = rightclass Solution: def zigzagLevelOrder(self, root: Optional[TreeNode]) -> List[List[int]]: # bfs => 큐로 if not root: return [] res = [..

637. Average of Levels in Binary Tree # 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 = rightclass Solution: def averageOfLevels(self, root: Optional[TreeNode]) -> List[float]: """ # BFS..로..큐로 풀자 """ res = [] que = deque([root]) ..

222. Count Complete Tree Nodes DFS, 재귀로 품# 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 = rightclass Solution: def countNodes(self, root: Optional[TreeNode]) -> int: def dfs(node): if not node: return 0 retu..

129. Sum Root to Leaf Numbers # 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 = rightclass Solution: def sumNumbers(self, root: Optional[TreeNode]) -> int: stack = [] def dfs(node, curString): if not node: return ..

114. Flatten Binary Tree to Linked List # 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 = rightclass Solution: def flatten(self, root: Optional[TreeNode]) -> None: """ Do not return anything, modify root in-place instead. """ # preorder..

117. Populating Next Right Pointers in Each Node II https://youtu.be/68RmOoq-OSs?si=-Ss1BuJuc5nIqS5A """# Definition for a Node.class Node: def __init__(self, val: int = 0, left: 'Node' = None, right: 'Node' = None, next: 'Node' = None): self.val = val self.left = left self.right = right self.next = next"""# 큐로 품class Solution: def connect(self, root: 'Node') ->..

106. Construct Binary Tree from Inorder and Postorder Traversal # 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 = rightclass Solution: def buildTree(self, inorder: List[int], postorder: List[int]) -> Optional[TreeNode]: # inorder: 왼, 중, 오 # postoder:..

226. Invert Binary Tree https://youtu.be/OnSn2XEQ4MY?si=M8XrLJXb_NV2PHRw 정말 쉽고, 기본적인 문제라는데, .. 그리고, DFS 로.. , DFS 이면,, 재귀로.. # 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 = rightclass Solution: def invertTree(self, root: Optional[TreeNode]) -> Optional[TreeNode]..

86. Partition List class Solution: def partition(self, head: Optional[ListNode], x: int) -> Optional[ListNode]: """ x 기준값보다, 작은 더미 노드 리스트, 큰 더미 노드 리스트를 만들어서 이어주기 """ # 작은 값 리스트와 큰 값 리스트의 더미 노드 생성 small_dummy = ListNode(0) large_dummy = ListNode(0) # 포인터 초기화 small = small_dummy # 작은 값 리스트의 끝 large = large_dummy # ..

61. Rotate List # Definition for singly-linked list.# class ListNode:# def __init__(self, val=0, next=None):# self.val = val# self.next = nextclass Solution: def rotateRight(self, head: Optional[ListNode], k: int) -> Optional[ListNode]: if not head or not head.next or k == 0: # 예외 처리: 리스트가 비었거나 노드가 하나인 경우 return head # 1. 리스트 길이 계산 length =..