꿈꾸는공학도

https://leetcode.com/problems/reverse-linked-list/description/Given the head of a singly linked list, reverse the list, and return the reversed list. Example 1:Input: head = [1,2,3,4,5]Output: [5,4,3,2,1]Example 2:Input: head = [1,2]Output: [2,1]Example 3:Input: head = []Output: [] Constraints:The number of nodes in the list is the range [0, 5000].-5000 Follow up: A linked list can be reversed e..

https://leetcode.com/problems/design-hashmap/description/Design a HashMap without using any built-in hash table libraries.Implement the MyHashMap class:MyHashMap() initializes the object with an empty map.void put(int key, int value) inserts a (key, value) pair into the HashMap. If the key already exists in the map, update the corresponding value.int get(int key) returns the value to which the s..

https://leetcode.com/problems/removing-minimum-number-of-magic-beans/description/You are given an array of positive integers beans, where each integer represents the number of magic beans found in a particular magic bag.Remove any number of beans (possibly none) from each bag such that the number of beans in each remaining non-empty bag (still containing at least one bean) is equal. Once a bean ..

https://leetcode.com/problems/n-ary-tree-level-order-traversal/description/Given an n-ary tree, return the level order traversal of its nodes' values.Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples). Example 1:Input: root = [1,null,3,2,4,null,5,6]Output: [[1],[3,2,4],[5,6]]Example 2:Input: root = [1,..

https://leetcode.com/problems/semi-ordered-permutation/You are given a 0-indexed permutation of n integers nums.A permutation is called semi-ordered if the first number equals 1 and the last number equals n. You can perform the below operation as many times as you want until you make nums a semi-ordered permutation:Pick two adjacent elements in nums, then swap them.Return the minimum number of o..

https://leetcode.com/problems/longest-non-decreasing-subarray-from-two-arrays/You are given two 0-indexed integer arrays nums1 and nums2 of length n.Let's define another 0-indexed integer array, nums3, of length n. For each index i in the range [0, n - 1], you can assign either nums1[i] or nums2[i] to nums3[i].Your task is to maximize the length of the longest non-decreasing subarray in nums3 by..

https://leetcode.com/problems/largest-odd-number-in-string/description/You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string "" if no odd integer exists.A substring is a contiguous sequence of characters within a string. Example 1:Input: num = "52"Output: "5"Explanation: The only non-..

https://leetcode.com/problems/build-array-from-permutation/Given a zero-based permutation nums (0-indexed), build an array ans of the same length where ans[i] = nums[nums[i]] for each 0  and return it.A zero-based permutation nums is an array of distinct integers from 0 to nums.length - 1 (inclusive). Example 1:Input: nums = [0,2,1,5,3,4]Output: [0,1,2,4,5,3]Explanation: The array ans is built a..

https://leetcode.com/problems/taking-maximum-energy-from-the-mystic-dungeon/description/In a mystic dungeon, n magicians are standing in a line. Each magician has an attribute that gives you energy. Some magicians can give you negative energy, which means taking energy from you.You have been cursed in such a way that after absorbing energy from magician i, you will be instantly transported to ma..

https://leetcode.com/problems/find-the-index-of-the-first-occurrence-in-a-string/description/Given two strings needle and haystack, return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1:Input: haystack = "sadbutsad", needle = "sad"Output: 0Explanation: "sad" occurs at index 0 and 6.The first occurrence is at index 0, so we return 0.Exa..