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547. Number of Provinces class Solution: def findCircleNum(self, isConnected: List[List[int]]) -> int: # dfs 로.. # init n = len(isConnected) province = 0 visited = [False]*n def dfs(cur_node_number: int): visited[cur_node_number] = True for neighbor in range(n): if isConnected[cur_node_number][neighbor] == 1 and vi..

450. Delete Node in a BST # 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 deleteNode(self, root: Optional[TreeNode], key: int) -> Optional[TreeNode]: if not root: return root if root.val key: # key 가 더 작으면, 왼쪽으로..

700. Search in a Binary Search 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 searchBST(self, root: Optional[TreeNode], val: int) -> Optional[TreeNode]: # node.val == val 인 node return cur = root while cur: ..

199. Binary Tree Right Side View # 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 rightSideView(self, root: Optional[TreeNode]) -> List[int]: if not root: # return root, null 을 반환하면 안되고, []을 반환해야함 return [] ..

1448. Count Good Nodes in Binary Tree https://youtu.be/7cp5imvDzl4?si=6kO3CQDgpb403ogg # 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 goodNodes(self, root: TreeNode) -> int: def dfs(node, maxVal): """ ..

104. Maximum Depth of Binary Tree https://youtu.be/meKRO8w6KT8?si=dDC-xWB8fOBdng6_ 1. 스텍을 이용: 깊이 우선 탐색 할때 주로 스텍을 사용스텍에, [(노드값, 깊이), ...] 이런식으로 추가스텍 팝 하고.. 그 자식노드를 스텍에 추가.. 하는 식으로..time: O(n)space: O(n) ```# 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```cla..

2130. Maximum Twin Sum of a Linked List Reverse 뒤집은 노드 만들기curr = head # 원래 리스트의 시작prev = None # 뒤집힌 리스트의 시작 (처음엔 없음)while curr: next = curr.next # 다음 노드 기억 curr.next = prev # 현재 노드의 방향을 뒤집음 prev = curr # prev를 현재 노드로 업데이트 curr = next # 다음 노드로 이동 이 루프가 끝나면:curr은 None (즉, 리스트 끝을 넘은 상태)prev는 뒤집힌 리스트의 시작 지점, 즉 새로운 head!🔍 예를 들어서:리스트가 1 → 2 → 3 ..

206. Reverse Linked List https://leetcode.com/problems/reverse-linked-list/description/  나도 stack 으로 풀었으나, 제대로 못푼 느낌??# Definition for singly-linked list.# class ListNode:# def __init__(self, val=0, next=None):# self.val = val# self.next = nextclass Solution: def reverseList(self, head: Optional[ListNode]) -> Optional[ListNode]: # 스텍으로 푸는 법 stack = [] ..

1679. Max Number of K-Sum Pairs You are given an integer array nums and an integer k.In one operation, you can pick two numbers from the array whose sum equals k and remove them from the array.Return the maximum number of operations you can perform on the array. Example 1:Input: nums = [1,2,3,4], k = 5Output: 2Explanation: Starting with nums = [1,2,3,4]:- Remove numbers 1 and 4, then nums = [2,3..

11. Container With Most Water You are given an integer array height of length n. There are n vertical lines drawn such that the two endpoints of the ith line are (i, 0) and (i, height[i]).Find two lines that together with the x-axis form a container, such that the container contains the most water.Return the maximum amount of water a container can store.Notice that you may not slant the containe..