문제Given a string s, return the longest palindromic substring in s.예시Example 1:Input: s = "babad" Output: "bab" Explanation: "aba" is also a valid answer.Example 2:Input: s = "cbbd" Output: "bb"조건1 s consist of only digits and English letters.답문자열을 순회하면서 각 인덱스마다 양옆으로 하위 문자열을 확장하면서 팰린드롬인지 판단합니다. 문자열 길이가 짝수일 때와 홀수일 때 두 가지 모양의 팰린드롬이 존재하므로, 각 인덱스마다 인덱스 번호 [i]를 중심으로 하는 경우와 [i, i+1]를 중심으로 하는 경우 두가지의 팰린..

문제A phrase is a palindrome if, after converting all uppercase letters into lowercase letters and removing all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include letters and numbers.Given a string s, return true if it is a palindrome, or false otherwise.예시Example 1:Input: s = "A man, a plan, a canal: Panama" Output: true Explanation: "amanaplanaca..

문제Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring, return the empty string "".The testcases will be generated such that the answer is unique.예시Example 1:Input: s = "ADOBECODEBANC", t = "ABC" Output: "BANC" Explanation: The minimum wind..

문제You are given a string s and an integer k. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most k times.Return the length of the longest substring containing the same letter you can get after performing the above operations.예시Example 1:Input: s = "ABAB", k = 2 Output: 4 Explanation: Replace the two 'A's with t..

문제You are given an n x n 2D matrix representing an image, rotate the image by 90 degrees (clockwise).You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.예시Example 1.Input: matrix = [[1,2,3],[4,5,6],[7,8,9]] Output: [[7,4,1],[8,5,2],[9,6,3]] Example 2.Input: matrix = [[5,1,9,11],[2,4,8,10],[13,3,..

문제You are given the head of a singly linked-list. The list can be represented as:L0 → L1 → … → Ln - 1 → LnReorder the list to be on the following form:L0 → Ln → L1 → Ln - 1 → L2 → Ln - 2 → …You may not modify the values in the list's nodes. Only nodes themselves may be changed.예시Example 1: Input: head = [1,2,3,4] Output: [1,4,2,3] Example 2: Input: head = [1,2,3,4,5] Output: [1,5,2,4,3]조건The num..

문제You are given an array of k linked-lists lists, each linked-list is sorted in ascending order.Merge all the linked-lists into one sorted linked-list and return it.예시Example 1:Input: lists = [[1,4,5],[1,3,4],[2,6]] Output: [1,1,2,3,4,4,5,6] Explanation: The linked-lists are: [ 1->4->5, 1->3->4, 2->6 ] merging them into one sorted list: 1->1->2->3->4->4->5->6Example 2:Input: lists = [] Out..

문제Given head, the head of a linked list, determine if the linked list has a cycle in it.There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Internally, pos is used to denote the index of the node that tail's next pointer is connected to. Note that pos is not passed as a parameter.Return true if there is a cycle..