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Jupyter notebook으로 Python code를 짜는 작업을 할 때, Python Module 들을 Local에 일일히 다 저장하면 은근히 용량도 많이 차지하고, 그것보다 문제인건 가끔 Module 간 Version 차이가 발생해 Module Import 시 Error가 발생한다. 소이 뻑이간 상태인데, 이게 한 두 건이면 그냥 무시하고 쓰는데 머신러닝 세계에선 Import 해야하는 Module이 생각보다 많다. 그래서 그냥 Google Colab으로 코드를 짜기도 한다. 대신, Google Colab은 기본적으로 Temporary 한 VM환경이기 때문에 Colab 세션을 껐다 킬 때는 설치했던 Package들이 모두 사라진다. 그리하여, 기본적으로 CELL 안에 pip install같은 코드를..

def smallest_pos_int(arr:list[int]) -> int: s = set() # 1) 양의 정수만 s 에 저장 for num in arr: if num > 0: s.add(num) # 2) 1부터 n+1까지 차례대로 s에 존재하는지 확인 n = len(arr) # 정답은 잘 해봐야 n+1이다..................... for i in range(1, n+2): # n+1 까지 확인, range 범위를 위해 n+2 if i not in s: # 집합 membership check: 평균 O(1) return i # 위 for문에서 항상 return이 ..

https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/description/Given the head of a singly linked list where elements are sorted in ascending order, convert it to a height-balanced binary search tree. Example 1:Input: head = [-10,-3,0,5,9]Output: [0,-3,9,-10,null,5]Explanation: One possible answer is [0,-3,9,-10,null,5], which represents the shown height balanced BST.Example ..

https://leetcode.com/problems/subtree-of-another-tree/description/Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise.A subtree of a binary tree tree is a tree that consists of a node in tree and all of this node's descendants. The tree tree could also be considered as a subtree of ..

https://leetcode.com/problems/combination-sum/description/Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.The same number may be chosen from candidates an unlimited number of times. Two combinations are unique if the frequency of ..

https://leetcode.com/problems/subsets/description/Given an integer array nums of unique elements, return all possible subsets (the power set).The solution set must not contain duplicate subsets. Return the solution in any order. Example 1:Input: nums = [1,2,3]Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]Example 2:Input: nums = [0]Output: [[],[0]] Constraints:1 -10 All the numbers of nums ar..

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order. Example 1:Input: nums = [1,2,3]Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]Example 2:Input: nums = [0,1]Output: [[0,1],[1,0]]Example 3:Input: nums = [1]Output: [[1]] Constraints:1 -10 All the integers of nums are unique.뭔가 기본적인 컨셉의 문제인데, 이게 또 한 번쯤은 집고 넘어가줘야 찝찝한게 없다..

https://leetcode.com/problems/reverse-linked-list-ii/description/Given the head of a singly linked list and two integers left and right where left  left to position right, and return the reversed list. Example 1:Input: head = [1,2,3,4,5], left = 2, right = 4Output: [1,4,3,2,5]Example 2:Input: head = [5], left = 1, right = 1Output: [5] Constraints:The number of nodes in the list is n.1 -500 1  Fo..

https://leetcode.com/problems/swapping-nodes-in-a-linked-list/description/You are given the head of a linked list, and an integer k.Return the head of the linked list after swapping the values of the kth node from the beginning and the kth node from the end (the list is 1-indexed). Example 1:Input: head = [1,2,3,4,5], k = 2Output: [1,4,3,2,5]Example 2:Input: head = [7,9,6,6,7,8,3,0,9,5], k = 5Ou..

https://leetcode.com/problems/maximum-employees-to-be-invited-to-a-meeting/description/?envType=daily-question&envId=2025-01-26A company is organizing a meeting and has a list of n employees, waiting to be invited. They have arranged for a large circular table, capable of seating any number of employees.The employees are numbered from 0 to n - 1. Each employee has a favorite person and they will..