开源第一周算法练习2

1.

234.Palindrome Linked List My Submissions QuestionEditorial Solution

Total Accepted: 43522 Total Submissions: 156746 Difficulty: Easy

Given a singly linked list, determine if it is a palindrome.

Follow up:

Could you do it in O(n) time and O(1) space?

2.

1. Permutations My Submissions QuestionEditorial Solution
   Total Accepted: 94379 Total Submissions: 266955 Difficulty: Medium
   Given a collection of distinct numbers, return all possible permutations.

   For example,
   [1,2,3] have the following permutations:
   [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

   3.

2. Permutations II

   Given a collection of numbers that might contain duplicates, return all possible unique permutations.

   For example,
   [1,1,2] have the following unique permutations:
   [1,1,2], [1,2,1], and [2,1,1].

   4.
   Reverse Nodes in k-Group

   Given a linked list, reverse the nodes of a linked list k at a time and return its modified 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 not alter the values in the nodes, only nodes itself may be changed.

   Only constant memory is allowed.

   For example,
   Given this linked list: 1->2->3->4->5

   For k = 2, you should return: 2->1->4->3->5

   For k = 3, you should return: 3->2->1->4->5