Alan 的筆記本

25. Reverse Nodes in k-Group https://leetcode.com/problems/reverse-nodes-in-k-group/ HardGiven the head of a linked list, reverse the nodes of the list k at a time, and return the modified list. k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes, in the end, should remain as it is. You may

70. Climbing Stairs https://leetcode.com/problems/climbing-stairs/ EasyYou are climbing a staircase. It takes n steps to reach the top. Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?   Example 1: Input: n = 2 Output: 2 Explanation: There are two ways to climb to the top. 1. 1 step + 1 step 2. 2 steps Example 2: Input: n

69. Sqrt(x) https://leetcode.com/problems/sqrtx/ EasyGiven a non-negative integer x, compute and return the square root of x. Since the return type is an integer, the decimal digits are truncated, and only the integer part of the result is returned. Note: You are not allowed to use any built-in exponent function or operator, such as pow(x, 0.5) or x ** 0.5.   Example 1: Input: x = 4 Output: 2 Example 2: Input: x = 8 Output:

433. Minimum Genetic Mutation https://leetcode.com/problems/minimum-genetic-mutation/ MediumA gene string can be represented by an 8-character long string, with choices from 'A', 'C', 'G', and 'T'. Suppose we need to investigate a mutation from a gene string start to a gene string end where one mutation is defined as one single character changed in the gene string. For example, "AACCGGTT" --> "AACCGGTA" is one mutation. There is also a gene bank bank

23. Merge k Sorted Lists https://leetcode.com/problems/merge-k-sorted-lists/ HardYou 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.   Example 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->6 Example 2: Input: lists = [] Output: [] Example 3: Input: lists