꿈꾸는공학도

https://leetcode.com/problems/count-ways-to-build-good-strings/description/?envType=daily-question&envId=2024-12-30Given the integers zero, one, low, and high, we can construct a string by starting with an empty string, and then at each step perform either of the following:Append the character '0' zero times.Append the character '1' one times.This can be performed any number of times.A good stri..

https://leetcode.com/problems/maximum-frequency-stack/description/Design a stack-like data structure to push elements to the stack and pop the most frequent element from the stack.Implement the FreqStack class:FreqStack() constructs an empty frequency stack.void push(int val) pushes an integer val onto the top of the stack.int pop() removes and returns the most frequent element in the stack.If t..

https://leetcode.com/problems/best-sightseeing-pair/description/?envType=daily-question&envId=2024-12-27You are given an integer array values where values[i] represents the value of the ith sightseeing spot. Two sightseeing spots i and j have a distance j - i between them.The score of a pair (i  values[i] + values[j] + i - j: the sum of the values of the sightseeing spots, minus the distance bet..

Algorithm Part의 기본적인 Data Structure인 Heap에 대해서 Implementation 연습을 시작해본다. Heap의 경우 Priority Queue라고도 생각하면 되고, Max/Min Heap으로 구분된다. 특징으론 Max Heap을 예로 들었을 때, Heap Data 구조에 입력되는 Data는 크기가 큰 순서(Max)대로 우선순위를 갖은 체 저장된다. 이 말은, Heap에서 특정 Data를 꺼낼 때(Deque) 가장 크기가 큰 녀석이 추출되는 것이다. 일반적으로 우리가 아는 queue구조에서 우선 순위만 선입선출이 아닌, Data 크기에 따라 결정된다는 것을 알고 있으면 된다. 따라서, 내부에 저장된 Data를 임의로 Search 할 수는 없지만 우리가 정한 Logic( Max..

https://leetcode.com/problems/target-sum/description/?envType=daily-question&envId=2024-12-26You are given an integer array nums and an integer target.You want to build an expression out of nums by adding one of the symbols '+' and '-' before each integer in nums and then concatenate all the integers.For example, if nums = [2, 1], you can add a '+' before 2 and a '-' before 1 and concatenate the..

https://leetcode.com/problems/find-minimum-diameter-after-merging-two-trees/description/?envType=daily-question&envId=2024-12-24There exist two undirected trees with n and m nodes, numbered from 0 to n - 1 and from 0 to m - 1, respectively. You are given two 2D integer arrays edges1 and edges2 of lengths n - 1 and m - 1, respectively, where edges1[i] = [ai, bi] indicates that there is an edge be..

https://leetcode.com/problems/minimum-number-of-operations-to-sort-a-binary-tree-by-level/description/?envType=daily-question&envId=2024-12-23You are given the root of a binary tree with unique values.In one operation, you can choose any two nodes at the same level and swap their values.Return the minimum number of operations needed to make the values at each level sorted in a strictly increasin..

class Solution: def leftmostBuildingQueries(self, heights: List[int], queries: List[List[int]]) -> List[int]: ans = [] # O(n^2 sol..) for i in range(len(queries)): # low & high are index high = max(queries[i]) low = min(queries[i]) if high == low or heights[high] > heights[low] : ans.append(high) co..

https://leetcode.com/problems/next-permutation/description/A permutation of an array of integers is an arrangement of its members into a sequence or linear order.For example, for arr = [1,2,3], the following are all the permutations of arr: [1,2,3], [1,3,2], [2, 1, 3], [2, 3, 1], [3,1,2], [3,2,1].The next permutation of an array of integers is the next lexicographically greater permutation of it..

문제의 요지와 Skleton code는 아래와 같다."""1. binary tree height 구하라2. binary tree balanced 맞는지 체크3. binary search tree 맞는지 체크4. 두 노드의 common ancestor 모두 구하기5. 두 노드의 lowest common ancestor 구하기"""  일단 문제에 쓰인 저 단어들이 각 무엇을 뜻하는지 부터 체크해보기1. height(T0)트리의 높이 구하기:정의: 트리의 높이는 루트 노드에서 가장 깊은 리프 노드까지의 경로 길이입니다.계산:루트 8의 왼쪽 서브트리의 높이 = 2루트 8의 오른쪽 서브트리의 높이 = 2따라서 전체 높이는 3.2. is_balanced(T0)트리가 균형 잡혔는지 여부:정의: 이진 트리가 균형 잡혔..