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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]: cur = root while cur: if cur.val == val: ..

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..

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..

392. Is Subsequence Given two strings s and t, return true if s is a subsequence of t, or false otherwise.A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not). Example 1:Input: s = "abc", ..

283. Move Zeroes Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements.Note that you must do this in-place without making a copy of the array. Example 1:Input: nums = [0,1,0,3,12]Output: [1,3,12,0,0]Example 2:Input: nums = [0]Output: [0] Constraints:1 -2^31  Follow up: Could you minimize the total number of operations done? 문제 풀이..

443. String Compression Given an array of characters chars, compress it using the following algorithm:Begin with an empty string s. For each group of consecutive repeating characters in chars:If the group's length is 1, append the character to s.Otherwise, append the character followed by the group's length.The compressed string s should not be returned separately, but instead, be stored in the ..